feat(pdf): replace PdfLib with Pdfium for form handling and general rendering tasks (#5899)

# Description of Changes

Improves PDF rendering in the viewer by adding digital signature field
support,
cleaning up overlay rendering, and migrating the contrast tool off
pdf-lib to PDFium WASM.

### Signature Field Overlay
- Added `SignatureFieldOverlay` component that renders digital signature
form fields
- Renders appearance streams when present; shows a fallback badge for
unsigned fields
- Uses PDFium WASM for bitmap extraction

### Overlay Rendering
- Integrated `SignatureFieldOverlay` and `ButtonAppearanceOverlay` into
`LocalEmbedPDF`
- Overlays are now clipped to page boundaries
- Clarified in `EmbedPdfViewer` that frontend overlays use PDFium WASM,
  backend overlays use PDFBox

### Contrast Tool Migration
- Replaced pdf-lib with PDFium WASM in `useAdjustContrastOperation`
- PDF page creation and image embedding now go through PDFium APIs
directly
- Updated bitmap handling and memory management accordingly

### Cleanup
- Fixed import ordering in viewer components
- Removed stale comments in the contrast operation hook

<!--
Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Signed-off-by: Balázs Szücs <bszucs1209@gmail.com>
Co-authored-by: Reece Browne <74901996+reecebrowne@users.noreply.github.com>

frontend/src/core/components/viewer/EmbedPdfViewer.tsx

@@ -20,12 +20,11 @@ import { isStirlingFile, getFormFillFileId } from '@app/types/fileContext';
 import { useViewerRightRailButtons } from '@app/components/viewer/useViewerRightRailButtons';
 import { StampPlacementOverlay } from '@app/components/viewer/StampPlacementOverlay';
 import { RulerOverlay, type PageMeasureScales, type PageScaleInfo, type ViewportScale } from '@app/components/viewer/RulerOverlay';
+import type { PDFDict, PDFNumber } from '@cantoo/pdf-lib';
 import { useWheelZoom } from '@app/hooks/useWheelZoom';
 import { useFormFill } from '@app/tools/formFill/FormFillContext';
 import { FormSaveBar } from '@app/tools/formFill/FormSaveBar';
 
-import type { PDFDict, PDFNumber } from '@cantoo/pdf-lib';
-
 // ─── Measure dictionary extraction ────────────────────────────────────────────
 
 async function extractPageMeasureScales(file: Blob): Promise<PageMeasureScales | null> {
@@ -38,7 +37,7 @@ async function extractPageMeasureScales(file: Blob): Promise<PageMeasureScales |
       if (!(measureObj instanceof PDFDict)) return null;
       const rObj = measureObj.lookup(PDFName.of('R'));
       const ratioLabel = (rObj instanceof PDFString || rObj instanceof PDFHexString)
-        ? rObj.decodeText() : '';
+              ? rObj.decodeText() : '';
       // D = distance array, X = x-axis fallback
       let fmtArray = measureObj.lookup(PDFName.of('D'));
       if (!(fmtArray instanceof PDFArray)) fmtArray = measureObj.lookup(PDFName.of('X'));
@@ -213,7 +212,7 @@ const EmbedPdfViewerContent = ({
   const isFormFillToolActive = (selectedTool as string) === 'formFill';
 
   // Form overlays are shown in BOTH modes:
-  // - Normal viewer: form overlays visible (pdf-lib, frontend-only)
+  // - Normal viewer: form overlays visible (PDFium WASM, frontend-only)
   // - formFill tool: form overlays visible (PDFBox, backend)
   const shouldEnableFormFill = true;
 
@@ -881,7 +880,7 @@ const EmbedPdfViewerContent = ({
   useViewerRightRailButtons(isRulerActive, setIsRulerActive);
 
   // Auto-fetch form fields when a PDF is loaded in the viewer.
-  // In normal viewer mode, this uses pdf-lib (frontend-only).
+  // In normal viewer mode, this uses PDFium WASM (frontend-only).
   // In formFill tool mode, this uses PDFBox (backend).
   const formFillFileIdRef = useRef<string | null>(null);
   const formFillProviderRef = useRef(isFormFillToolActive);

frontend/src/core/components/viewer/LocalEmbedPDF.tsx

@@ -61,6 +61,8 @@ import { DocumentReadyWrapper } from '@app/components/viewer/DocumentReadyWrappe
 import { ActiveDocumentProvider } from '@app/components/viewer/ActiveDocumentContext';
 import { absoluteWithBasePath } from '@app/constants/app';
 import { FormFieldOverlay } from '@app/tools/formFill/FormFieldOverlay';
+import { ButtonAppearanceOverlay } from '@app/tools/formFill/ButtonAppearanceOverlay';
+import SignatureFieldOverlay from '@app/components/viewer/SignatureFieldOverlay';
 import { CommentsSidebar } from '@app/components/viewer/CommentsSidebar';
 import { CommentAuthorProvider } from '@app/contexts/CommentAuthorContext';
 import { accountService } from '@app/services/accountService';
@@ -770,6 +772,7 @@ export function LocalEmbedPDF({ file, url, fileName, enableAnnotations = false,
                             width,
                             height,
                             position: 'relative',
+                            overflow: 'hidden', // clip overlays (buttons, fields) that extend beyond the page rect
                             userSelect: 'none',
                             WebkitUserSelect: 'none',
                             MozUserSelect: 'none',
@@ -790,6 +793,16 @@ export function LocalEmbedPDF({ file, url, fileName, enableAnnotations = false,
                           </div>
                           <TextSelectionHandler documentId={documentId} pageIndex={pageIndex} />
 
+                          {/* ButtonAppearanceOverlay — renders PDF-native button visuals as bitmaps */}
+                          {enableFormFill && file && (
+                            <ButtonAppearanceOverlay
+                              pageIndex={pageIndex}
+                              pdfSource={file}
+                              pageWidth={width}
+                              pageHeight={height}
+                            />
+                          )}
+
                           {/* FormFieldOverlay for interactive form filling */}
                           {enableFormFill && (
                             <FormFieldOverlay
@@ -801,6 +814,17 @@ export function LocalEmbedPDF({ file, url, fileName, enableAnnotations = false,
                             />
                           )}
 
+                          {/* SignatureFieldOverlay — bitmaps of digital-signature appearances */}
+                          {file && (
+                            <SignatureFieldOverlay
+                              documentId={documentId}
+                              pageIndex={pageIndex}
+                              pdfSource={file}
+                              pageWidth={width}
+                              pageHeight={height}
+                            />
+                          )}
+
                           {/* AnnotationLayer for annotation editing and annotation-based redactions */}
                           {(enableAnnotations || enableRedaction) && (
                             <AnnotationLayer

frontend/src/core/components/viewer/SignatureFieldOverlay.tsx

@@ -0,0 +1,250 @@
+/**
+ * SignatureFieldOverlay — Renders digital-signature form fields on top of a
+ * PDF page.
+ *
+ * When a signature widget has an appearance stream (i.e. a visible graphic
+ * embedded by the signing tool), we render it via `EPDF_RenderAnnotBitmap`
+ * (an @embedpdf PDFium WASM extension) and paint the result into a `<canvas>`
+ * positioned at the correct overlay location.  This is the same rendering
+ * path the engine itself uses for individual annotation bitmaps.
+ *
+ * For widgets without an appearance stream (unsigned fields, or fields whose
+ * PDF writer didn't embed one), we fall back to a translucent badge overlay.
+ */
+import React, { useEffect, useMemo, useRef, useState, memo } from 'react';
+import {
+  renderSignatureFieldAppearances,
+  extractSignatures,
+  type SignatureFieldAppearance,
+} from '@app/services/pdfiumService';
+
+interface SignatureFieldOverlayProps {
+  pageIndex: number;
+  /** URL or File for the current PDF — used to extract signature data. */
+  pdfSource: File | Blob | null;
+  /** Document ID from EmbedPDF (kept for caller compatibility). */
+  documentId: string;
+  /** Rendered page width from Scroller (pixel space). */
+  pageWidth: number;
+  /** Rendered page height from Scroller (pixel space). */
+  pageHeight: number;
+}
+
+interface ResolvedSignatureField extends SignatureFieldAppearance {
+  /** Whether a cryptographic signature was found for this field. */
+  isSigned: boolean;
+  /** Signer reason string (if available). */
+  reason?: string;
+  /** Signing time string (if available). */
+  time?: string;
+}
+let _cachedSource: File | Blob | null = null;
+let _cachedFields: ResolvedSignatureField[] = [];
+let _cachePromise: Promise<ResolvedSignatureField[]> | null = null;
+
+async function resolveFields(
+  source: File | Blob,
+): Promise<ResolvedSignatureField[]> {
+  if (source === _cachedSource && _cachePromise) return _cachePromise;
+  _cachedSource = source;
+
+  _cachePromise = (async () => {
+    const buf = await source.arrayBuffer();
+    const [appearances, signatures] = await Promise.all([
+      renderSignatureFieldAppearances(buf),
+      extractSignatures(buf),
+    ]);
+
+    return appearances.map((f, i) => {
+      // Positional correlation is only reliable when both arrays have the same
+      // length — i.e. one signature object per signature field in document order.
+      // When the counts differ we cannot safely attribute reason/time per-field,
+      // so we fall back to a whole-document "is signed" indicator.
+      const exactMatch = appearances.length === signatures.length;
+      const matchedSig = exactMatch ? signatures[i] : undefined;
+      return {
+        ...f,
+        isSigned: exactMatch ? i < signatures.length : signatures.length > 0,
+        reason: matchedSig?.reason,
+        time: matchedSig?.time,
+      };
+    });
+
+  })();
+
+  _cachedFields = await _cachePromise;
+  return _cachedFields;
+}
+
+function SignatureBitmapCanvas({
+  imageData,
+  cssWidth,
+  cssHeight,
+}: {
+  imageData: ImageData;
+  cssWidth: number;
+  cssHeight: number;
+}) {
+  const canvasRef = useRef<HTMLCanvasElement>(null);
+
+  useEffect(() => {
+    const canvas = canvasRef.current;
+    if (!canvas) return;
+    canvas.width = imageData.width;
+    canvas.height = imageData.height;
+    const ctx = canvas.getContext('2d');
+    if (ctx) ctx.putImageData(imageData, 0, 0);
+  }, [imageData]);
+
+  return (
+    <canvas
+      ref={canvasRef}
+      style={{
+        width: cssWidth,
+        height: cssHeight,
+        display: 'block',
+      }}
+    />
+  );
+}
+
+function SignatureFieldOverlayInner({
+  pageIndex,
+  pdfSource,
+  documentId: _documentId,
+  pageWidth,
+  pageHeight,
+}: SignatureFieldOverlayProps) {
+  const [fields, setFields] = useState<ResolvedSignatureField[]>([]);
+
+  useEffect(() => {
+    if (!pdfSource) {
+      setFields([]);
+      return;
+    }
+    let cancelled = false;
+    resolveFields(pdfSource).then((res) => {
+      if (!cancelled) setFields(res);
+    }).catch(() => {
+      if (!cancelled) setFields([]);
+    });
+    return () => { cancelled = true; };
+  }, [pdfSource]);
+
+  const pageFields = useMemo(
+    () => fields.filter((f) => f.pageIndex === pageIndex),
+    [fields, pageIndex],
+  );
+
+  if (pageFields.length === 0) return null;
+
+  return (
+    <div
+      style={{
+        position: 'absolute',
+        top: 0,
+        left: 0,
+        width: '100%',
+        height: '100%',
+        pointerEvents: 'none',
+        zIndex: 6,
+      }}
+      data-signature-overlay-page={pageIndex}
+    >
+      {pageFields.map((field, idx) => {
+        // Use the source PDF page dimensions that the extraction used for
+        // coordinate computation. This avoids mismatches with pdfPage.size
+        // from EmbedPDF which may report different dimensions.
+        const sx = field.sourcePageWidth  > 0 ? pageWidth  / field.sourcePageWidth  : 1;
+        const sy = field.sourcePageHeight > 0 ? pageHeight / field.sourcePageHeight : 1;
+        const left = field.x * sx;
+        const top = field.y * sy;
+        const width = field.width * sx;
+        const height = field.height * sy;
+
+        // If we have a rendered appearance bitmap, paint it via <canvas>.
+        if (field.imageData) {
+          return (
+            <div
+              key={`sig-${field.fieldName}-${idx}`}
+              style={{
+                position: 'absolute',
+                left,
+                top,
+                width,
+                height,
+                overflow: 'hidden',
+                pointerEvents: 'auto',
+                cursor: 'default',
+              }}
+              title={
+                field.isSigned
+                  ? `Signed${field.reason ? `: ${field.reason}` : ''}${field.time ? ` (${field.time})` : ''}`
+                  : `Signature field: ${field.fieldName}`
+              }
+            >
+              <SignatureBitmapCanvas
+                imageData={field.imageData}
+                cssWidth={width}
+                cssHeight={height}
+              />
+            </div>
+          );
+        }
+
+        // Fallback: translucent badge for fields without an appearance.
+        return (
+          <div
+            key={`sig-${field.fieldName}-${idx}`}
+            style={{
+              position: 'absolute',
+              left,
+              top,
+              width,
+              height,
+              border: field.isSigned
+                ? '2px solid rgba(34, 139, 34, 0.7)'
+                : '2px dashed rgba(180, 180, 180, 0.7)',
+              borderRadius: 4,
+              background: field.isSigned
+                ? 'rgba(34, 139, 34, 0.08)'
+                : 'rgba(200, 200, 200, 0.08)',
+              display: 'flex',
+              alignItems: 'center',
+              justifyContent: 'center',
+              overflow: 'hidden',
+              pointerEvents: 'auto',
+              cursor: 'default',
+            }}
+            title={
+              field.isSigned
+                ? `Signed${field.reason ? `: ${field.reason}` : ''}${field.time ? ` (${field.time})` : ''}`
+                : `Unsigned signature field: ${field.fieldName}`
+            }
+          >
+            <span
+              style={{
+                fontSize: Math.min(height * 0.35, 14),
+                color: field.isSigned ? 'rgba(34, 139, 34, 0.85)' : 'rgba(120, 120, 120, 0.85)',
+                fontWeight: 600,
+                textAlign: 'center',
+                lineHeight: 1.2,
+                padding: '2px 4px',
+                userSelect: 'none',
+                whiteSpace: 'nowrap',
+                textOverflow: 'ellipsis',
+                overflow: 'hidden',
+                maxWidth: '100%',
+              }}
+            >
+              {field.isSigned ? '🔒 Signed' : '✎ Signature'}
+            </span>
+          </div>
+        );
+      })}
+    </div>
+  );
+}
+
+const SignatureFieldOverlay = memo(SignatureFieldOverlayInner);
+export default SignatureFieldOverlay;

frontend/src/core/hooks/tools/adjustContrast/useAdjustContrastOperation.ts

@@ -1,10 +1,14 @@
 import { useTranslation } from 'react-i18next';
 import { ToolType, useToolOperation, CustomProcessorResult } from '@app/hooks/tools/shared/useToolOperation';
 import { AdjustContrastParameters, defaultParameters } from '@app/hooks/tools/adjustContrast/useAdjustContrastParameters';
-import { PDFDocument as PDFLibDocument } from '@cantoo/pdf-lib';
 import { applyAdjustmentsToCanvas } from '@app/components/tools/adjustContrast/utils';
 import { pdfWorkerManager } from '@app/services/pdfWorkerManager';
 import { createFileFromApiResponse } from '@app/utils/fileResponseUtils';
+import {
+  getPdfiumModule,
+  saveRawDocument,
+} from '@app/services/pdfiumService';
+import { copyRgbaToBgraHeap } from '@app/utils/pdfiumBitmapUtils';
 
 async function renderPdfPageToCanvas(pdf: any, pageNumber: number, scale: number): Promise<HTMLCanvasElement> {
   const page = await pdf.getPage(pageNumber);
@@ -18,37 +22,94 @@ async function renderPdfPageToCanvas(pdf: any, pageNumber: number, scale: number
   return canvas;
 }
 
-// adjustment logic moved to shared util
-
-// Render, adjust, and assemble all pages of a single PDF into a new PDF
+// Render, adjust, and assemble all pages of a single PDF into a new PDF using PDFium
 async function buildAdjustedPdfForFile(file: File, params: AdjustContrastParameters): Promise<File> {
+    const m = await getPdfiumModule();
     const arrayBuffer = await file.arrayBuffer();
     const pdf = await pdfWorkerManager.createDocument(arrayBuffer, {});
     const pageCount = pdf.numPages;
 
-    const newDoc = await PDFLibDocument.create();
+    const docPtr = m.FPDF_CreateNewDocument();
+    if (!docPtr) throw new Error('PDFium: failed to create document');
 
-    for (let p = 1; p <= pageCount; p++) {
-      const srcCanvas = await renderPdfPageToCanvas(pdf, p, 2);
-      const adjusted = applyAdjustmentsToCanvas(srcCanvas, params);
-      const pngUrl = adjusted.toDataURL('image/png');
-      const res = await fetch(pngUrl);
-      const pngBytes = new Uint8Array(await res.arrayBuffer());
-      const embedded = await newDoc.embedPng(pngBytes);
-      const { width, height } = embedded.scale(1);
-      const page = newDoc.addPage([width, height]);
-      page.drawImage(embedded, { x: 0, y: 0, width, height });
+    try {
+      for (let p = 1; p <= pageCount; p++) {
+        const srcCanvas = await renderPdfPageToCanvas(pdf, p, 2);
+        const adjusted = applyAdjustmentsToCanvas(srcCanvas, params);
+        const ctx = adjusted.getContext('2d');
+        if (!ctx) {
+          console.warn(`[adjustContrast] Skipping page ${p}: failed to get canvas context`);
+          continue;
+        }
+
+        const imageData = ctx.getImageData(0, 0, adjusted.width, adjusted.height);
+        const imgWidth = imageData.width;
+        const imgHeight = imageData.height;
+
+        // Since we render at scale 2, the actual PDF page size is half
+        const pdfPageWidth = imgWidth / 2;
+        const pdfPageHeight = imgHeight / 2;
+
+        const pagePtr = m.FPDFPage_New(docPtr, p - 1, pdfPageWidth, pdfPageHeight);
+        if (!pagePtr) {
+          console.warn(`[adjustContrast] Skipping page ${p}: failed to create PDFium page`);
+          continue;
+        }
+
+        let bitmapPtr = 0;
+        try {
+          bitmapPtr = m.FPDFBitmap_Create(imgWidth, imgHeight, 1);
+          if (!bitmapPtr) {
+            console.warn(`[adjustContrast] Skipping page ${p}: failed to create bitmap`);
+            continue;
+          }
+
+          const bufferPtr = m.FPDFBitmap_GetBuffer(bitmapPtr);
+          const stride = m.FPDFBitmap_GetStride(bitmapPtr);
+          copyRgbaToBgraHeap(m, new Uint8Array(imageData.data.buffer), bufferPtr, imgWidth, imgHeight, stride);
+
+          const imageObjPtr = m.FPDFPageObj_NewImageObj(docPtr);
+          if (imageObjPtr) {
+            const setBitmapOk = m.FPDFImageObj_SetBitmap(pagePtr, 0, imageObjPtr, bitmapPtr);
+            if (setBitmapOk) {
+              const matrixPtr = m.pdfium.wasmExports.malloc(6 * 4);
+              try {
+                m.pdfium.setValue(matrixPtr, pdfPageWidth, 'float');
+                m.pdfium.setValue(matrixPtr + 4, 0, 'float');
+                m.pdfium.setValue(matrixPtr + 8, 0, 'float');
+                m.pdfium.setValue(matrixPtr + 12, pdfPageHeight, 'float');
+                m.pdfium.setValue(matrixPtr + 16, 0, 'float');
+                m.pdfium.setValue(matrixPtr + 20, 0, 'float');
+
+                if (m.FPDFPageObj_SetMatrix(imageObjPtr, matrixPtr)) {
+                  m.FPDFPage_InsertObject(pagePtr, imageObjPtr);
+                } else {
+                  m.FPDFPageObj_Destroy(imageObjPtr);
+                }
+              } finally {
+                m.pdfium.wasmExports.free(matrixPtr);
+              }
+            } else {
+              m.FPDFPageObj_Destroy(imageObjPtr);
+            }
+          }
+        } finally {
+          if (bitmapPtr) m.FPDFBitmap_Destroy(bitmapPtr);
+          m.FPDFPage_GenerateContent(pagePtr);
+          m.FPDF_ClosePage(pagePtr);
+        }
+      }
+
+      const pdfBytes = await saveRawDocument(docPtr);
+      const out = createFileFromApiResponse(pdfBytes, { 'content-type': 'application/pdf' }, file.name);
+      pdfWorkerManager.destroyDocument(pdf);
+      return out;
+    } finally {
+      m.FPDF_CloseDocument(docPtr);
     }
-
-    const pdfBytes = await newDoc.save();
-    const out = createFileFromApiResponse(pdfBytes, { 'content-type': 'application/pdf' }, file.name);
-    pdfWorkerManager.destroyDocument(pdf);
-    return out;
 }
 
 async function processPdfClientSide(params: AdjustContrastParameters, files: File[]): Promise<CustomProcessorResult> {
-  // Limit concurrency to avoid exhausting memory/CPU while still getting speedups
-  // Heuristic: use up to 4 workers on capable machines, otherwise 2-3
   let CONCURRENCY_LIMIT = 2;
   if (typeof navigator !== 'undefined' && typeof navigator.hardwareConcurrency === 'number') {
     if (navigator.hardwareConcurrency >= 8) CONCURRENCY_LIMIT = 4;
@@ -85,7 +146,6 @@ export const adjustContrastOperationConfig = {
   customProcessor: processPdfClientSide,
   operationType: 'adjustContrast',
   defaultParameters,
-  // Single-step settings component for Automate
   settingsComponentPath: 'components/tools/adjustContrast/AdjustContrastSingleStepSettings',
 } as const;
 
@@ -96,4 +156,3 @@ export const useAdjustContrastOperation = () => {
     getErrorMessage: () => t('adjustContrast.error.failed', 'Failed to adjust colors/contrast')
   });
 };
-

frontend/src/core/hooks/tools/removeAnnotations/useRemoveAnnotationsOperation.ts

@@ -2,73 +2,49 @@ import { useTranslation } from 'react-i18next';
 import { useToolOperation, ToolType, CustomProcessorResult } from '@app/hooks/tools/shared/useToolOperation';
 import { createStandardErrorHandler } from '@app/utils/toolErrorHandler';
 import { RemoveAnnotationsParameters, defaultParameters } from '@app/hooks/tools/removeAnnotations/useRemoveAnnotationsParameters';
-import { PDFDocument, PDFName, PDFRef, PDFDict } from '@cantoo/pdf-lib';
-// Client-side PDF processing using PDF-lib
+import {
+  getPdfiumModule,
+  openRawDocumentSafe,
+  closeDocAndFreeBuffer,
+  saveRawDocument,
+} from '@app/services/pdfiumService';
+
+// Client-side PDF processing using PDFium WASM
 const removeAnnotationsProcessor = async (_parameters: RemoveAnnotationsParameters, files: File[]): Promise<CustomProcessorResult> => {
   const processedFiles: File[] = [];
 
   for (const file of files) {
     try {
-      // Load the PDF
+      const m = await getPdfiumModule();
       const fileArrayBuffer = await file.arrayBuffer();
-      const pdfBytesIn = new Uint8Array(fileArrayBuffer);
-      const pdfDoc = await PDFDocument.load(pdfBytesIn, { ignoreEncryption: true });
-      const ctx = pdfDoc.context;
+      const docPtr = await openRawDocumentSafe(fileArrayBuffer);
 
-      const pages = pdfDoc.getPages();
-      for (let i = 0; i < pages.length; i++) {
-        const page = pages[i];
-
-        // Annots() returns PDFArray | undefined
-        const annots = page.node.Annots();
-        if (!annots || annots.size() === 0) continue;
-
-        // Delete each annotation object (they are usually PDFRef)
-        for (let j = annots.size() - 1; j >= 0; j--) {
-          try {
-            const entry = annots.get(j);
-            if (entry instanceof PDFRef) {
-              ctx.delete(entry);
-            } else if (entry instanceof PDFDict) {
-              // In practice, Annots array should contain refs; if not, just remove the array linkage.
-              // (We avoid poking internal maps to find a ref for the dict.)
-            }
-          } catch (err) {
-            console.warn(`Failed to remove annotation ${j} on page ${i + 1}:`, err);
-          }
-        }
-
-        // Remove the Annots key entirely
-        try {
-          if (page.node.has(PDFName.of('Annots'))) {
-            page.node.delete(PDFName.of('Annots'));
-          }
-        } catch (err) {
-          console.warn(`Failed to delete /Annots on page ${i + 1}:`, err);
-        }
-      }
-
-      // Optional: if removing ALL annotations across the doc, strip AcroForm to avoid dangling widget refs
       try {
-        const catalog = pdfDoc.context.lookup(pdfDoc.context.trailerInfo.Root);
-        if (catalog && 'has' in catalog && 'delete' in catalog) {
-          const catalogDict = catalog as any;
-          if (catalogDict.has(PDFName.of('AcroForm'))) {
-            catalogDict.delete(PDFName.of('AcroForm'));
+        const pageCount = m.FPDF_GetPageCount(docPtr);
+
+        for (let i = 0; i < pageCount; i++) {
+          const pagePtr = m.FPDF_LoadPage(docPtr, i);
+          if (!pagePtr) continue;
+
+          // Remove all annotations from the page (iterate backward)
+          const annotCount = m.FPDFPage_GetAnnotCount(pagePtr);
+          for (let j = annotCount - 1; j >= 0; j--) {
+            try {
+              m.FPDFPage_RemoveAnnot(pagePtr, j);
+            } catch (err) {
+              console.warn(`Failed to remove annotation ${j} on page ${i + 1}:`, err);
+            }
           }
+
+          m.FPDF_ClosePage(pagePtr);
         }
-      } catch (err) {
-        console.warn('Failed to remove /AcroForm:', err);
+
+        const outBytes = await saveRawDocument(docPtr);
+        const processedFile = new File([outBytes], file.name, { type: 'application/pdf' });
+        processedFiles.push(processedFile);
+      } finally {
+        closeDocAndFreeBuffer(m, docPtr);
       }
-
-      // Save returns Uint8Array — safe for Blob
-      const outBytes = await pdfDoc.save();
-      const outBlob = new Blob([new Uint8Array(outBytes)], { type: 'application/pdf' });
-
-      // Create new file with original name
-      const processedFile = new File([outBlob], file.name, { type: 'application/pdf' });
-
-      processedFiles.push(processedFile);
     } catch (error) {
       console.error('Error processing file:', file.name, error);
       throw new Error(

frontend/src/core/hooks/tools/validateSignature/outputtedPDFSections/CenteredMessageSection.ts

@@ -1,11 +1,11 @@
-import { PDFFont, PDFPage, rgb } from '@cantoo/pdf-lib';
+import { PdfiumFont, PdfiumPage, rgb } from '@app/services/pdfiumDocBuilder';
 import { wrapText } from '@app/hooks/tools/validateSignature/utils/pdfText';
 import { colorPalette } from '@app/hooks/tools/validateSignature/utils/pdfPalette';
 
 interface DrawCenteredMessageOptions {
-  page: PDFPage;
-  font: PDFFont;
-  fontBold: PDFFont;
+  page: PdfiumPage;
+  font: PdfiumFont;
+  fontBold: PdfiumFont;
   text: string;
   description: string;
   marginX: number;

frontend/src/core/hooks/tools/validateSignature/outputtedPDFSections/FieldBoxSection.ts

@@ -1,11 +1,11 @@
-import { PDFFont, PDFPage } from '@cantoo/pdf-lib';
+import { PdfiumFont, PdfiumPage } from '@app/services/pdfiumDocBuilder';
 import { wrapText } from '@app/hooks/tools/validateSignature/utils/pdfText';
 import { colorPalette } from '@app/hooks/tools/validateSignature/utils/pdfPalette';
 
 interface FieldBoxOptions {
-  page: PDFPage;
-  font: PDFFont;
-  fontBold: PDFFont;
+  page: PdfiumPage;
+  font: PdfiumFont;
+  fontBold: PdfiumFont;
   x: number;
   top: number;
   width: number;

frontend/src/core/hooks/tools/validateSignature/outputtedPDFSections/SignatureSection.ts

@@ -1,5 +1,5 @@
 import type { TFunction } from 'i18next';
-import { PDFFont, PDFPage } from '@cantoo/pdf-lib';
+import { PdfiumFont, PdfiumPage } from '@app/services/pdfiumDocBuilder';
 import { SignatureValidationSignature } from '@app/types/validateSignature';
 import { drawFieldBox } from '@app/hooks/tools/validateSignature/outputtedPDFSections/FieldBoxSection';
 import { drawStatusBadge } from '@app/hooks/tools/validateSignature/outputtedPDFSections/StatusBadgeSection';
@@ -8,15 +8,15 @@ import { formatDate } from '@app/hooks/tools/validateSignature/utils/pdfText';
 import { colorPalette } from '@app/hooks/tools/validateSignature/utils/pdfPalette';
 
 interface DrawSignatureSectionOptions {
-  page: PDFPage;
+  page: PdfiumPage;
   cursorY: number;
   signature: SignatureValidationSignature;
   index: number;
   marginX: number;
   contentWidth: number;
   columnGap: number;
-  font: PDFFont;
-  fontBold: PDFFont;
+  font: PdfiumFont;
+  fontBold: PdfiumFont;
   t: TFunction<'translation'>;
 }
 
@@ -106,7 +106,7 @@ export const drawSignatureSection = ({
     thickness: 1,
     color: colorPalette.boxBorder,
   });
-  nextY -= 20; 
+  nextY -= 20;
 
   const certificateFields = [
     { label: t('validateSignature.cert.issuer', 'Issuer'), value: signature.issuerDN || '-' },

frontend/src/core/hooks/tools/validateSignature/outputtedPDFSections/StatusBadgeSection.ts

@@ -1,9 +1,9 @@
-import { PDFFont, PDFPage, rgb } from '@cantoo/pdf-lib';
+import { PdfiumFont, PdfiumPage, rgb } from '@app/services/pdfiumDocBuilder';
 
 interface StatusBadgeOptions {
-  page: PDFPage;
-  font: PDFFont;
-  fontBold: PDFFont;
+  page: PdfiumPage;
+  font: PdfiumFont;
+  fontBold: PdfiumFont;
   text: string;
   x: number;
   y: number;

frontend/src/core/hooks/tools/validateSignature/outputtedPDFSections/SummarySection.ts

@@ -1,5 +1,5 @@
 import type { TFunction } from 'i18next';
-import { PDFFont, PDFImage, PDFPage } from '@cantoo/pdf-lib';
+import { PdfiumFont, PdfiumImage, PdfiumPage } from '@app/services/pdfiumDocBuilder';
 import { SignatureValidationReportEntry } from '@app/types/validateSignature';
 import { drawFieldBox } from '@app/hooks/tools/validateSignature/outputtedPDFSections/FieldBoxSection';
 import { drawThumbnailImage, drawThumbnailPlaceholder } from '@app/hooks/tools/validateSignature/outputtedPDFSections/ThumbnailSection';
@@ -7,17 +7,17 @@ import { colorPalette } from '@app/hooks/tools/validateSignature/utils/pdfPalett
 import { formatFileSize } from '@app/hooks/tools/validateSignature/utils/pdfText';
 
 interface DrawSummarySectionOptions {
-  page: PDFPage;
+  page: PdfiumPage;
   cursorY: number;
   entry: SignatureValidationReportEntry;
-  font: PDFFont;
-  fontBold: PDFFont;
+  font: PdfiumFont;
+  fontBold: PdfiumFont;
   marginX: number;
   contentWidth: number;
   columnGap: number;
   statusText: string;
   statusColor: (typeof colorPalette)['success'];
-  loadThumbnail: (url: string) => Promise<{ image: PDFImage } | null>;
+  loadThumbnail: (url: string) => Promise<{ image: PdfiumImage } | null>;
   t: TFunction<'translation'>;
 }
 

frontend/src/core/hooks/tools/validateSignature/outputtedPDFSections/ThumbnailSection.ts

@@ -1,9 +1,9 @@
-import { PDFFont, PDFPage, PDFImage } from '@cantoo/pdf-lib';
+import { PdfiumFont, PdfiumPage, PdfiumImage } from '@app/services/pdfiumDocBuilder';
 import { colorPalette } from '@app/hooks/tools/validateSignature/utils/pdfPalette';
 
 export const drawThumbnailPlaceholder = (
-  page: PDFPage,
-  fontBold: PDFFont,
+  page: PdfiumPage,
+  fontBold: PdfiumFont,
   x: number,
   top: number,
   width: number,
@@ -35,8 +35,8 @@ export const drawThumbnailPlaceholder = (
 };
 
 export const drawThumbnailImage = (
-  page: PDFPage,
-  image: PDFImage,
+  page: PdfiumPage,
+  image: PdfiumImage,
   x: number,
   top: number,
   width: number,

frontend/src/core/hooks/tools/validateSignature/signatureReportPdf.ts

@@ -1,4 +1,4 @@
-import { PDFDocument, PDFPage, StandardFonts } from '@cantoo/pdf-lib';
+import { PdfiumDocument, PdfiumPage, StandardFonts } from '@app/services/pdfiumDocBuilder';
 import type { TFunction } from 'i18next';
 import { SignatureValidationReportEntry } from '@app/types/validateSignature';
 import { REPORT_PDF_FILENAME } from '@app/hooks/tools/validateSignature/utils/signatureUtils';
@@ -16,7 +16,7 @@ const MARGIN_Y = 22;
 const CONTENT_WIDTH = PAGE_WIDTH - MARGIN_X * 2;
 const COLUMN_GAP = 18;
 
-const drawDivider = (page: PDFPage, marginX: number, contentWidth: number, y: number) => {
+const drawDivider = (page: PdfiumPage, marginX: number, contentWidth: number, y: number) => {
   page.drawLine({
     start: { x: marginX, y },
     end: { x: marginX + contentWidth, y },
@@ -29,7 +29,7 @@ export const createReportPdf = async (
   entries: SignatureValidationReportEntry[],
   t: TFunction<'translation'>
 ): Promise<File> => {
-  const doc = await PDFDocument.create();
+  const doc = await PdfiumDocument.create();
   const font = await doc.embedFont(StandardFonts.Helvetica);
   const fontBold = await doc.embedFont(StandardFonts.HelveticaBold);
   const loadThumbnail = createThumbnailLoader(doc);
@@ -101,7 +101,6 @@ export const createReportPdf = async (
     }
 
     for (let i = 0; i < entry.signatures.length; i += 1) {
-      // After the first signature, start a new page per signature
       if (i > 0) {
         ({ page, cursorY } = startReportPage({
           doc,

frontend/src/core/hooks/tools/validateSignature/utils/pdfPageHelpers.ts

@@ -1,11 +1,11 @@
-import { PDFDocument, PDFFont, PDFImage } from '@cantoo/pdf-lib';
+import { PdfiumDocument, PdfiumFont, PdfiumImage } from '@app/services/pdfiumDocBuilder';
 import type { TFunction } from 'i18next';
 import { colorPalette } from '@app/hooks/tools/validateSignature/utils/pdfPalette';
 
 interface StartPageParams {
-  doc: PDFDocument;
-  font: PDFFont;
-  fontBold: PDFFont;
+  doc: PdfiumDocument;
+  font: PdfiumFont;
+  fontBold: PdfiumFont;
   marginX: number;
   marginY: number;
   contentWidth: number;
@@ -63,8 +63,8 @@ export const startReportPage = ({
   return { page, cursorY };
 };
 
-export const createThumbnailLoader = (doc: PDFDocument) => {
-  const cache = new Map<string, { image: PDFImage } | null>();
+export const createThumbnailLoader = (doc: PdfiumDocument) => {
+  const cache = new Map<string, { image: PdfiumImage } | null>();
 
   return async (url: string) => {
     if (cache.has(url)) {
@@ -75,7 +75,7 @@ export const createThumbnailLoader = (doc: PDFDocument) => {
       const response = await fetch(url);
       const bytes = new Uint8Array(await response.arrayBuffer());
       const contentType = response.headers.get('content-type') || '';
-      let image: PDFImage;
+      let image: PdfiumImage;
 
       if (contentType.includes('png')) {
         image = await doc.embedPng(bytes);

frontend/src/core/hooks/tools/validateSignature/utils/pdfPalette.ts

@@ -1,4 +1,4 @@
-import { rgb } from '@cantoo/pdf-lib';
+import { rgb } from '@app/services/pdfiumDocBuilder';
 
 type RgbTuple = [number, number, number];
 
@@ -21,7 +21,7 @@ const defaultLightPalette: Record<
 const toRgb = ([r, g, b]: RgbTuple) => rgb(r / 255, g / 255, b / 255);
 
 /**
- * Utility function to get CSS variable values and convert them to pdf-lib RGB format.
+ * Utility function to get CSS variable values and convert them to RGB format.
  * Falls back to sensible defaults when the CSS variable cannot be resolved.
  */
 function getCssVariableAsRgb(variableName: string, fallback: RgbTuple) {

frontend/src/core/hooks/tools/validateSignature/utils/pdfText.ts

@@ -1,6 +1,6 @@
-import { PDFFont } from '@cantoo/pdf-lib';
+import { PdfiumFont } from '@app/services/pdfiumDocBuilder';
 
-export const wrapText = (text: string, font: PDFFont, fontSize: number, maxWidth: number): string[] => {
+export const wrapText = (text: string, font: PdfiumFont, fontSize: number, maxWidth: number): string[] => {
   const lines: string[] = [];
   const paragraphs = text.split(/\r?\n/);
 

frontend/src/core/hooks/usePdfLibLinks.ts

@@ -1,7 +1,4 @@
 import { useState, useEffect, useRef } from 'react';
-import {
-  PDFDocument,
-} from '@cantoo/pdf-lib';
 import {
   PdfLibLink,
   extractLinksFromPage,
@@ -20,14 +17,14 @@ export interface PdfLibLinksResult {
 }
 
 interface CachedDoc {
-  doc: PDFDocument;
+  data: ArrayBuffer;
   /** Number of active consumers (hook instances) holding this entry. */
   refCount: number;
   /** Per-page extracted links (lazy, filled on first request). */
   pageLinks: Map<number, { links: PdfLibLink[]; width: number; height: number }>;
-  /** Set to true when the PDF catalog/pages tree is invalid, so we
+  /** Set to true when the PDF is invalid, so we
    *  skip link extraction on all subsequent calls without retrying. */
-  invalidCatalog?: boolean;
+  invalidDocument?: boolean;
 }
 
 const docCache = new Map<string, Promise<CachedDoc>>();
@@ -37,13 +34,8 @@ async function acquireDocument(url: string): Promise<CachedDoc> {
     const promise = (async (): Promise<CachedDoc> => {
       const response = await fetch(url);
       const buffer = await response.arrayBuffer();
-      const doc = await PDFDocument.load(new Uint8Array(buffer), {
-        ignoreEncryption: true,
-        updateMetadata: false,
-        throwOnInvalidObject: false,
-      });
 
-      return { doc, refCount: 0, pageLinks: new Map() };
+      return { data: buffer, refCount: 0, pageLinks: new Map() };
     })();
     docCache.set(url, promise);
 
@@ -107,7 +99,7 @@ export function usePdfLibLinks(
           return;
         }
 
-        if (cached.invalidCatalog) {
+        if (cached.invalidDocument) {
           setResult({ links: [], pdfPageWidth: 0, pdfPageHeight: 0, loading: false });
           releaseDocument(url);
           return;
@@ -115,27 +107,12 @@ export function usePdfLibLinks(
 
         let pageData = cached.pageLinks.get(pageIndex);
         if (!pageData) {
-          let pageCount: number;
           try {
-            pageCount = cached.doc.getPageCount();
-          } catch {
-            cached.invalidCatalog = true;
-            setResult({ links: [], pdfPageWidth: 0, pdfPageHeight: 0, loading: false });
-            releaseDocument(url);
-            return;
-          }
-
-          if (pageIndex < 0 || pageIndex >= pageCount) {
-            setResult({ links: [], pdfPageWidth: 0, pdfPageHeight: 0, loading: false });
-            releaseDocument(url);
-            return;
-          }
-
-          try {
-            const page = cached.doc.getPage(pageIndex);
-            const { width, height } = page.getSize();
-            const links = extractLinksFromPage(cached.doc, page, pageIndex);
-            pageData = { links, width, height };
+            const { links, pdfPageWidth, pdfPageHeight } = await extractLinksFromPage(
+              cached.data,
+              pageIndex,
+            );
+            pageData = { links, width: pdfPageWidth, height: pdfPageHeight };
             cached.pageLinks.set(pageIndex, pageData);
           } catch (pageError) {
             console.warn(`[usePdfLibLinks] Failed to read page ${pageIndex}:`, pageError);

frontend/src/core/services/pdfExportService.ts

@@ -1,7 +1,19 @@
-import { PDFDocument as PDFLibDocument, degrees, PageSizes } from '@cantoo/pdf-lib';
+import {
+  getPdfiumModule,
+  openRawDocumentSafe,
+  closeRawDocument,
+  saveRawDocument,
+  importPages,
+  setPageRotation,
+  addNewPage,
+} from '@app/services/pdfiumService';
 import { downloadFile } from '@app/services/downloadService';
 import { PDFDocument, PDFPage } from '@app/types/pageEditor';
 
+// A4 dimensions in PDF points (72 dpi)
+const A4_WIDTH = 595.276;
+const A4_HEIGHT = 841.890;
+
 export interface ExportOptions {
   selectedOnly?: boolean;
   filename?: string;
@@ -19,7 +31,6 @@ export class PDFExportService {
     const { selectedOnly = false, filename } = options;
 
     try {
-      // Determine which pages to export
       const pagesToExport = selectedOnly && selectedPageIds.length > 0
         ? pdfDocument.pages.filter(page => selectedPageIds.includes(page.id))
         : pdfDocument.pages;
@@ -28,10 +39,8 @@ export class PDFExportService {
         throw new Error('No pages to export');
       }
 
-      // Load original PDF and create new document
       const originalPDFBytes = await pdfDocument.file.arrayBuffer();
-      const sourceDoc = await PDFLibDocument.load(originalPDFBytes, { ignoreEncryption: true });
-      const blob = await this.createSingleDocument(sourceDoc, pagesToExport);
+      const blob = await this.createSingleDocument(originalPDFBytes, pagesToExport);
       const exportFilename = this.generateFilename(filename || pdfDocument.name);
 
       return { blob, filename: exportFilename };
@@ -56,7 +65,6 @@ export class PDFExportService {
     const { selectedOnly = false, filename } = options;
 
     try {
-      // Determine which pages to export
       const pagesToExport = selectedOnly && selectedPageIds.length > 0
         ? pdfDocument.pages.filter(page => selectedPageIds.includes(page.id))
         : pdfDocument.pages;
@@ -79,102 +87,140 @@ export class PDFExportService {
   }
 
   /**
-   * Create a PDF document from multiple source files
+   * Create a PDF document from multiple source files using PDFium WASM.
    */
   private async createMultiSourceDocument(
     sourceFiles: Map<string, File>,
     pages: PDFPage[]
   ): Promise<Blob> {
-    const newDoc = await PDFLibDocument.create();
+    const m = await getPdfiumModule();
+
+    // Create destination document
+    const destDocPtr = m.FPDF_CreateNewDocument();
+    if (!destDocPtr) throw new Error('PDFium: failed to create destination document');
 
     // Load all source documents once and cache them
-    const loadedDocs = new Map<string, PDFLibDocument>();
+    const loadedDocs = new Map<string, number>();
 
-    for (const [fileId, file] of sourceFiles) {
-      try {
-        const arrayBuffer = await file.arrayBuffer();
-        const doc = await PDFLibDocument.load(arrayBuffer, { ignoreEncryption: true });
-        loadedDocs.set(fileId, doc);
-      } catch (error) {
-        console.warn(`Failed to load source file ${fileId}:`, error);
-      }
-    }
-
-    for (const page of pages) {
-      if (page.isBlankPage || page.originalPageNumber === -1) {
-        // Create a blank page
-        const blankPage = newDoc.addPage(PageSizes.A4);
-
-        blankPage.setRotation(degrees(page.rotation));
-      } else if (page.originalFileId && loadedDocs.has(page.originalFileId)) {
-        // Get the correct source document for this page
-        const sourceDoc = loadedDocs.get(page.originalFileId)!;
-        const sourcePageIndex = page.originalPageNumber - 1;
-
-        if (sourcePageIndex >= 0 && sourcePageIndex < sourceDoc.getPageCount()) {
-          // Copy the page from the correct source document
-          const [copiedPage] = await newDoc.copyPages(sourceDoc, [sourcePageIndex]);
-
-          copiedPage.setRotation(degrees(page.rotation));
-
-          newDoc.addPage(copiedPage);
+    try {
+      for (const [fileId, file] of sourceFiles) {
+        try {
+          const arrayBuffer = await file.arrayBuffer();
+          const docPtr = await openRawDocumentSafe(arrayBuffer);
+          loadedDocs.set(fileId, docPtr);
+        } catch (error) {
+          console.warn(`Failed to load source file ${fileId}:`, error);
         }
-      } else {
-        console.warn(`Cannot find source document for page ${page.pageNumber} (fileId: ${page.originalFileId})`);
       }
+
+      let insertIdx = 0;
+      for (const page of pages) {
+        if (page.isBlankPage || page.originalPageNumber === -1) {
+          // Insert a blank A4 page
+          await addNewPage(destDocPtr, insertIdx, A4_WIDTH, A4_HEIGHT);
+          // Apply rotation
+          const pdfiumRotation = degreesToPdfiumRotation(page.rotation);
+          if (pdfiumRotation !== 0) {
+            await setPageRotation(destDocPtr, insertIdx, pdfiumRotation);
+          }
+          insertIdx++;
+        } else if (page.originalFileId && loadedDocs.has(page.originalFileId)) {
+          const srcDocPtr = loadedDocs.get(page.originalFileId)!;
+          const srcPageCount = m.FPDF_GetPageCount(srcDocPtr);
+          const sourcePageIndex = page.originalPageNumber - 1;
+
+          if (sourcePageIndex >= 0 && sourcePageIndex < srcPageCount) {
+            // Import the specific page (1-based page range for FPDF_ImportPages)
+            const pageRange = String(sourcePageIndex + 1);
+            const imported = await importPages(destDocPtr, srcDocPtr, pageRange, insertIdx);
+            if (!imported) {
+              console.warn(
+                `[PDFExport] importPages failed for fileId=${page.originalFileId} pageRange=${pageRange} — page will be missing from output.`,
+              );
+            }
+
+            // Apply rotation
+            const pdfiumRotation = degreesToPdfiumRotation(page.rotation);
+            if (pdfiumRotation !== 0) {
+              await setPageRotation(destDocPtr, insertIdx, pdfiumRotation);
+            }
+            insertIdx++;
+          }
+        } else {
+          console.warn(`Cannot find source document for page ${page.pageNumber} (fileId: ${page.originalFileId})`);
+        }
+      }
+
+      // Save the assembled document
+      const resultBuf = await saveRawDocument(destDocPtr);
+      return new Blob([resultBuf], { type: 'application/pdf' });
+    } finally {
+      // Cleanup all loaded source documents
+      for (const docPtr of loadedDocs.values()) {
+        await closeRawDocument(docPtr);
+      }
+      m.FPDF_CloseDocument(destDocPtr);
     }
-
-    // Set metadata
-    newDoc.setCreator('Stirling PDF');
-    newDoc.setProducer('Stirling PDF');
-    newDoc.setCreationDate(new Date());
-    newDoc.setModificationDate(new Date());
-
-    const pdfBytes = await newDoc.save();
-    return new Blob([pdfBytes as BlobPart], { type: 'application/pdf' });
   }
 
   /**
-   * Create a single PDF document with all operations applied (single source)
+   * Create a single PDF document with all operations applied (single source) using PDFium.
    */
   private async createSingleDocument(
-    sourceDoc: PDFLibDocument,
+    sourceData: ArrayBuffer,
     pages: PDFPage[]
   ): Promise<Blob> {
-    const newDoc = await PDFLibDocument.create();
+    const m = await getPdfiumModule();
 
-    for (const page of pages) {
-      if (page.isBlankPage || page.originalPageNumber === -1) {
-        // Create a blank page
-        const blankPage = newDoc.addPage(PageSizes.A4);
-
-        blankPage.setRotation(degrees(page.rotation));
-      } else {
-        // Get the original page from source document using originalPageNumber
-        const sourcePageIndex = page.originalPageNumber - 1;
-
-        if (sourcePageIndex >= 0 && sourcePageIndex < sourceDoc.getPageCount()) {
-          // Copy the page
-          const [copiedPage] = await newDoc.copyPages(sourceDoc, [sourcePageIndex]);
-
-          copiedPage.setRotation(degrees(page.rotation));
-
-          newDoc.addPage(copiedPage);
-        }
-      }
+    // Open source document
+    const srcDocPtr = await openRawDocumentSafe(sourceData);
+    const destDocPtr = m.FPDF_CreateNewDocument();
+    if (!destDocPtr) {
+      await closeRawDocument(srcDocPtr);
+      throw new Error('PDFium: failed to create destination document');
     }
 
-    // Set metadata
-    newDoc.setCreator('Stirling PDF');
-    newDoc.setProducer('Stirling PDF');
-    newDoc.setCreationDate(new Date());
-    newDoc.setModificationDate(new Date());
+    try {
+      const srcPageCount = m.FPDF_GetPageCount(srcDocPtr);
+      let insertIdx = 0;
 
-    const pdfBytes = await newDoc.save();
-    return new Blob([pdfBytes as BlobPart], { type: 'application/pdf' });
+      for (const page of pages) {
+        if (page.isBlankPage || page.originalPageNumber === -1) {
+          await addNewPage(destDocPtr, insertIdx, A4_WIDTH, A4_HEIGHT);
+          const pdfiumRotation = degreesToPdfiumRotation(page.rotation);
+          if (pdfiumRotation !== 0) {
+            await setPageRotation(destDocPtr, insertIdx, pdfiumRotation);
+          }
+          insertIdx++;
+        } else {
+          const sourcePageIndex = page.originalPageNumber - 1;
+
+          if (sourcePageIndex >= 0 && sourcePageIndex < srcPageCount) {
+            const pageRange = String(sourcePageIndex + 1);
+            const imported = await importPages(destDocPtr, srcDocPtr, pageRange, insertIdx);
+            if (!imported) {
+              console.warn(
+                `[PDFExport] importPages failed for page ${page.originalPageNumber} pageRange=${pageRange} — page will be missing from output.`,
+              );
+            }
+
+            const pdfiumRotation = degreesToPdfiumRotation(page.rotation);
+            if (pdfiumRotation !== 0) {
+              await setPageRotation(destDocPtr, insertIdx, pdfiumRotation);
+            }
+            insertIdx++;
+          }
+        }
+      }
+
+      const resultBuf = await saveRawDocument(destDocPtr);
+      return new Blob([resultBuf], { type: 'application/pdf' });
+    } finally {
+      await closeRawDocument(srcDocPtr);
+      m.FPDF_CloseDocument(destDocPtr);
+    }
   }
 
-
   /**
    * Generate appropriate filename for export
    */
@@ -183,7 +229,6 @@ export class PDFExportService {
     return `${baseName}.pdf`;
   }
 
-
   /**
    * Download a single file
    */
@@ -198,7 +243,7 @@ export class PDFExportService {
     blobs.forEach((blob, index) => {
       setTimeout(() => {
         this.downloadFile(blob, filenames[index]);
-      }, index * 500); // Stagger downloads
+      }, index * 500);
     });
   }
 
@@ -241,9 +286,8 @@ export class PDFExportService {
 
     const splitCount = pagesToExport.reduce((count, page) => {
       return count + (page.splitAfter ? 1 : 0);
-    }, 1); // At least 1 document
+    }, 1);
 
-    // Rough size estimation (very approximate)
     const avgPageSize = pdfDocument.file.size / pdfDocument.totalPages;
     const estimatedBytes = avgPageSize * pagesToExport.length;
     const estimatedSize = this.formatFileSize(estimatedBytes);
@@ -267,5 +311,18 @@ export class PDFExportService {
   }
 }
 
+/**
+ * Convert degrees (0, 90, 180, 270) to PDFium rotation enum (0, 1, 2, 3).
+ */
+function degreesToPdfiumRotation(degrees: number): number {
+  const normalized = ((degrees % 360) + 360) % 360;
+  switch (normalized) {
+    case 90: return 1;
+    case 180: return 2;
+    case 270: return 3;
+    default: return 0;
+  }
+}
+
 // Export singleton instance
 export const pdfExportService = new PDFExportService();

frontend/src/core/services/pdfWorkerManager.ts

@@ -34,6 +34,7 @@ class PDFWorkerManager {
         'pdfjs-dist/legacy/build/pdf.worker.min.mjs',
         import.meta.url
       ).toString();
+      (GlobalWorkerOptions as any).docBaseUrl = undefined;
       this.isInitialized = true;
     }
   }
@@ -74,13 +75,17 @@ class PDFWorkerManager {
         disableAutoFetch: options.disableAutoFetch ?? true,
         disableStream: options.disableStream ?? true,
         stopAtErrors: options.stopAtErrors ?? false,
-        verbosity: options.verbosity ?? 0
+        verbosity: options.verbosity ?? 0,
+        // Suppress warnings about unimplemented widget types and other non-critical issues
+        isEvalSupported: false,
       } : {
         ...pdfData,
         disableAutoFetch: options.disableAutoFetch ?? true,
         disableStream: options.disableStream ?? true,
         stopAtErrors: options.stopAtErrors ?? false,
-        verbosity: options.verbosity ?? 0
+        verbosity: options.verbosity ?? 0,
+        // Suppress warnings about unimplemented widget types and other non-critical issues
+        isEvalSupported: false,
       }
     );
 

frontend/src/core/services/pdfiumDocBuilder.ts

@@ -0,0 +1,405 @@
+/**
+ * pdfiumDocBuilder — High-level PDF document builder powered by PDFium WASM.
+ *
+ * Provides an API surface compatible with common pdf-lib patterns
+ * (drawText, drawRectangle, drawLine, drawImage, font metrics, etc.)
+ * so that code previously using pdf-lib for PDF *generation* can be
+ * migrated with minimal changes.
+ *
+ * Used by the signature validation report system.
+ */
+import { getPdfiumModule, writeUtf16, saveRawDocument } from '@app/services/pdfiumService';
+import { embedBitmapImageOnPage } from '@app/utils/pdfiumBitmapUtils';
+import type { WrappedPdfiumModule } from '@embedpdf/pdfium';
+
+// ---------------------------------------------------------------------------
+// Color type (replaces pdf-lib's `rgb()`)
+// ---------------------------------------------------------------------------
+
+export interface PdfiumColor {
+  _r: number;
+  _g: number;
+  _b: number;
+}
+
+/**
+ * Create an RGB color (each component 0–1). Drop-in replacement for pdf-lib's `rgb()`.
+ */
+export function rgb(r: number, g: number, b: number): PdfiumColor {
+  return { _r: r, _g: g, _b: b };
+}
+
+function colorToRGBA(c: PdfiumColor): [number, number, number, number] {
+  return [Math.round(c._r * 255), Math.round(c._g * 255), Math.round(c._b * 255), 255];
+}
+
+// ---------------------------------------------------------------------------
+// Font abstraction
+// ---------------------------------------------------------------------------
+
+/** Standard PDF font names matching pdf-lib's StandardFonts enum. */
+export const StandardFonts = {
+  Helvetica: 'Helvetica',
+  HelveticaBold: 'Helvetica-Bold',
+  HelveticaOblique: 'Helvetica-Oblique',
+  HelveticaBoldOblique: 'Helvetica-BoldOblique',
+  Courier: 'Courier',
+  CourierBold: 'Courier-Bold',
+  TimesRoman: 'Times-Roman',
+  TimesBold: 'Times-Bold',
+} as const;
+
+export class PdfiumFont {
+  readonly name: string;
+  private _canvas: OffscreenCanvas | HTMLCanvasElement | null = null;
+  private _ctx: CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D | null = null;
+
+  constructor(name: string) {
+    this.name = name;
+  }
+
+  /**
+   * Measure the width of `text` at the given `fontSize` (in PDF points).
+   * Uses canvas font metrics as a reliable cross-browser measurement.
+   */
+  widthOfTextAtSize(text: string, fontSize: number): number {
+    const ctx = this._getCtx();
+    ctx.font = `${fontSize}px "${this._cssFontFamily()}"`;
+    return ctx.measureText(text).width;
+  }
+
+  /**
+   * Returns the line height for a given font size (approximation).
+   */
+  heightAtSize(fontSize: number): number {
+    return fontSize * 1.2;
+  }
+
+  /** Map PDF font name to a CSS font-family for canvas measurement. */
+  private _cssFontFamily(): string {
+    if (this.name.startsWith('Helvetica')) return 'Helvetica, Arial, sans-serif';
+    if (this.name.startsWith('Courier')) return 'Courier, monospace';
+    if (this.name.startsWith('Times')) return 'Times New Roman, serif';
+    return 'sans-serif';
+  }
+
+  private _getCtx(): CanvasRenderingContext2D | OffscreenCanvasRenderingContext2D {
+    if (this._ctx) return this._ctx;
+    if (typeof OffscreenCanvas !== 'undefined') {
+      this._canvas = new OffscreenCanvas(1, 1);
+      this._ctx = this._canvas.getContext('2d')!;
+    } else {
+      this._canvas = document.createElement('canvas');
+      this._ctx = this._canvas.getContext('2d')!;
+    }
+    return this._ctx;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Image abstraction
+// ---------------------------------------------------------------------------
+
+export class PdfiumImage {
+  readonly width: number;
+  readonly height: number;
+  /** Raw RGBA pixel data */
+  readonly _rgba: Uint8Array;
+
+  constructor(rgba: Uint8Array, width: number, height: number) {
+    this._rgba = rgba;
+    this.width = width;
+    this.height = height;
+  }
+
+  /** Returns scaled dimensions (matches pdf-lib's `PDFImage.scale()`). */
+  scale(factor: number): { width: number; height: number } {
+    return { width: this.width * factor, height: this.height * factor };
+  }
+
+  /** Scale to fit within maxWidth × maxHeight preserving aspect ratio (matches pdf-lib's `PDFImage.scaleToFit()`). */
+  scaleToFit(maxWidth: number, maxHeight: number): { width: number; height: number } {
+    const ratio = Math.min(maxWidth / this.width, maxHeight / this.height, 1);
+    return { width: this.width * ratio, height: this.height * ratio };
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Page abstraction
+// ---------------------------------------------------------------------------
+
+export interface DrawTextOptions {
+  x: number;
+  y: number;
+  size: number;
+  font?: PdfiumFont;
+  color?: PdfiumColor;
+}
+
+export interface DrawRectangleOptions {
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+  color?: PdfiumColor;
+  borderColor?: PdfiumColor;
+  borderWidth?: number;
+  opacity?: number;
+}
+
+export interface DrawImageOptions {
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+}
+
+export interface DrawLineOptions {
+  start: { x: number; y: number };
+  end: { x: number; y: number };
+  thickness?: number;
+  color?: PdfiumColor;
+}
+
+export class PdfiumPage {
+  readonly _m: WrappedPdfiumModule;
+  readonly _docPtr: number;
+  readonly _pagePtr: number;
+  readonly width: number;
+  readonly height: number;
+
+  constructor(m: WrappedPdfiumModule, docPtr: number, pagePtr: number, width: number, height: number) {
+    this._m = m;
+    this._docPtr = docPtr;
+    this._pagePtr = pagePtr;
+    this.width = width;
+    this.height = height;
+  }
+
+  /**
+   * Draw text on the page. API compatible with pdf-lib's `PDFPage.drawText()`.
+   */
+  drawText(text: string, options: DrawTextOptions): void {
+    const { x, y, size, font, color } = options;
+    const m = this._m;
+    const fontName = font?.name ?? 'Helvetica';
+
+    const textObjPtr = m.FPDFPageObj_NewTextObj(this._docPtr, fontName, size);
+    if (!textObjPtr) return;
+
+    // Set text content (UTF-16)
+    const textPtr = writeUtf16(m, text);
+    m.FPDFText_SetText(textObjPtr, textPtr);
+    m.pdfium.wasmExports.free(textPtr);
+
+    // Set color
+    if (color) {
+      const [r, g, b, a] = colorToRGBA(color);
+      m.FPDFPageObj_SetFillColor(textObjPtr, r, g, b, a);
+    }
+
+    // Position the text object
+    // FPDFPageObj_Transform(obj, a, b, c, d, e, f) — applies affine transform
+    // Identity + translate: a=1, b=0, c=0, d=1, e=x, f=y
+    m.FPDFPageObj_Transform(textObjPtr, 1, 0, 0, 1, x, y);
+
+    m.FPDFPage_InsertObject(this._pagePtr, textObjPtr);
+  }
+
+  /**
+   * Draw a rectangle on the page. API compatible with pdf-lib's `PDFPage.drawRectangle()`.
+   */
+  drawRectangle(options: DrawRectangleOptions): void {
+    const { x, y, width, height, color, borderColor, borderWidth = 1 } = options;
+    const m = this._m;
+
+    const pathPtr = m.FPDFPageObj_CreateNewPath(x, y);
+    if (!pathPtr) return;
+
+    m.FPDFPath_LineTo(pathPtr, x + width, y);
+    m.FPDFPath_LineTo(pathPtr, x + width, y + height);
+    m.FPDFPath_LineTo(pathPtr, x, y + height);
+    m.FPDFPath_Close(pathPtr);
+
+    let hasFill = false;
+    let hasStroke = false;
+
+    if (color) {
+      const [r, g, b, a] = colorToRGBA(color);
+      m.FPDFPageObj_SetFillColor(pathPtr, r, g, b, a);
+      hasFill = true;
+    }
+
+    if (borderColor) {
+      const [r, g, b, a] = colorToRGBA(borderColor);
+      m.FPDFPageObj_SetStrokeColor(pathPtr, r, g, b, a);
+      m.FPDFPageObj_SetStrokeWidth(pathPtr, borderWidth);
+      hasStroke = true;
+    }
+
+    // Fill mode: 0 = none, 1 = alternate, 2 = winding
+    const fillMode = hasFill ? 1 : 0;
+    m.FPDFPath_SetDrawMode(pathPtr, fillMode, hasStroke);
+
+    m.FPDFPage_InsertObject(this._pagePtr, pathPtr);
+  }
+
+  /**
+   * Draw a line on the page. API compatible with pdf-lib's `PDFPage.drawLine()`.
+   */
+  drawLine(options: DrawLineOptions): void {
+    const { start, end, thickness = 1, color } = options;
+    const m = this._m;
+
+    const pathPtr = m.FPDFPageObj_CreateNewPath(start.x, start.y);
+    if (!pathPtr) return;
+
+    m.FPDFPath_LineTo(pathPtr, end.x, end.y);
+
+    if (color) {
+      const [r, g, b, a] = colorToRGBA(color);
+      m.FPDFPageObj_SetStrokeColor(pathPtr, r, g, b, a);
+    }
+    m.FPDFPageObj_SetStrokeWidth(pathPtr, thickness);
+
+    // fillMode=0 (no fill), stroke=true
+    m.FPDFPath_SetDrawMode(pathPtr, 0, true);
+
+    m.FPDFPage_InsertObject(this._pagePtr, pathPtr);
+  }
+
+  /**
+   * Draw an image on the page. API compatible with pdf-lib's `PDFPage.drawImage()`.
+   */
+  drawImage(image: PdfiumImage, options: DrawImageOptions): void {
+    const { x, y, width, height } = options;
+    embedBitmapImageOnPage(
+      this._m, this._docPtr, this._pagePtr,
+      { rgba: image._rgba, width: image.width, height: image.height },
+      x, y, width, height,
+    );
+  }
+
+  /** Finalize the page content stream. Called internally by PdfiumDocument. */
+  _generateContent(): void {
+    this._m.FPDFPage_GenerateContent(this._pagePtr);
+  }
+
+  /** Close the page pointer. Called internally by PdfiumDocument. */
+  _close(): void {
+    this._m.FPDF_ClosePage(this._pagePtr);
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Document abstraction
+// ---------------------------------------------------------------------------
+
+export class PdfiumDocument {
+  readonly _m: WrappedPdfiumModule;
+  readonly _docPtr: number;
+  private _pages: PdfiumPage[] = [];
+  private _fonts: Map<string, PdfiumFont> = new Map();
+
+  private constructor(m: WrappedPdfiumModule, docPtr: number) {
+    this._m = m;
+    this._docPtr = docPtr;
+  }
+
+  /** Create a new empty PDF document. Drop-in replacement for `PDFDocument.create()`. */
+  static async create(): Promise<PdfiumDocument> {
+    const m = await getPdfiumModule();
+    const docPtr = m.FPDF_CreateNewDocument();
+    if (!docPtr) throw new Error('PDFium: failed to create document');
+    return new PdfiumDocument(m, docPtr);
+  }
+
+  /** Add a new page to the document. */
+  addPage(dimensions: [number, number]): PdfiumPage {
+    const [width, height] = dimensions;
+    const insertIdx = this._pages.length;
+    const pagePtr = this._m.FPDFPage_New(this._docPtr, insertIdx, width, height);
+    if (!pagePtr) throw new Error('PDFium: failed to create page');
+    const page = new PdfiumPage(this._m, this._docPtr, pagePtr, width, height);
+    this._pages.push(page);
+    return page;
+  }
+
+  /** Embed a standard PDF font. Returns a PdfiumFont for text measurement and drawing. */
+  async embedFont(fontName: string): Promise<PdfiumFont> {
+    if (this._fonts.has(fontName)) return this._fonts.get(fontName)!;
+    const font = new PdfiumFont(fontName);
+    this._fonts.set(fontName, font);
+    return font;
+  }
+
+  /** Embed a PNG image from raw bytes. */
+  async embedPng(bytes: Uint8Array | ArrayBuffer): Promise<PdfiumImage> {
+    return this._decodeImage(bytes instanceof Uint8Array ? bytes : new Uint8Array(bytes), 'image/png');
+  }
+
+  /** Embed a JPEG image from raw bytes. */
+  async embedJpg(bytes: Uint8Array | ArrayBuffer): Promise<PdfiumImage> {
+    return this._decodeImage(bytes instanceof Uint8Array ? bytes : new Uint8Array(bytes), 'image/jpeg');
+  }
+
+  /** Get the number of pages. */
+  getPageCount(): number {
+    return this._pages.length;
+  }
+
+  /** Save the document and return the PDF bytes. */
+  async save(): Promise<Uint8Array> {
+    // Generate content for all pages before saving
+    for (const page of this._pages) {
+      page._generateContent();
+    }
+
+    const buf = await saveRawDocument(this._docPtr);
+
+    // Close all pages and the document
+    for (const page of this._pages) {
+      page._close();
+    }
+    this._m.FPDF_CloseDocument(this._docPtr);
+
+    return new Uint8Array(buf);
+  }
+
+  /**
+   * Decode image bytes to RGBA pixel data via canvas.
+   * PDFium's image object APIs require bitmap data.
+   */
+  private _decodeImage(bytes: Uint8Array, mimeType: string): Promise<PdfiumImage> {
+    return new Promise((resolve, reject) => {
+      const blob = new Blob([bytes as BlobPart], { type: mimeType });
+      const url = URL.createObjectURL(blob);
+      const img = new Image();
+      img.onload = () => {
+        try {
+          const canvas = document.createElement('canvas');
+          canvas.width = img.width;
+          canvas.height = img.height;
+          const ctx = canvas.getContext('2d');
+          if (!ctx) {
+            URL.revokeObjectURL(url);
+            reject(new Error('Canvas 2D context unavailable'));
+            return;
+          }
+          ctx.drawImage(img, 0, 0);
+          const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
+          URL.revokeObjectURL(url);
+          resolve(new PdfiumImage(new Uint8Array(imageData.data.buffer), canvas.width, canvas.height));
+        } catch (err) {
+          URL.revokeObjectURL(url);
+          reject(err);
+        }
+      };
+      img.onerror = () => {
+        URL.revokeObjectURL(url);
+        reject(new Error('Failed to decode image'));
+      };
+      img.src = url;
+    });
+  }
+}

frontend/src/core/styles/index.css

@@ -18,6 +18,19 @@ code {
     monospace;
 }
 
+/* Suppress font visibility warnings for PDF.js embedded fonts */
+@font-face {
+  font-family: 'Adwaita Mono';
+  src: local('Adwaita Mono');
+  font-display: optional;
+}
+
+@font-face {
+  font-family: 'Nimbus Mono PS';
+  src: local('Nimbus Mono PS');
+  font-display: optional;
+}
+
 /* CSS Variables */
 :root {
   --footer-height: 2rem;

frontend/src/core/tools/formFill/ButtonAppearanceOverlay.tsx

@@ -0,0 +1,121 @@
+/**
+ * ButtonAppearanceOverlay — Renders PDF push-button widget appearances as
+ * canvas bitmaps on top of a PDF page.
+ *
+ * This is a visual-only layer (pointerEvents: none). Click handling is done
+ * separately by FormFieldOverlay's transparent hit-target divs.
+ *
+ * Uses the same EPDF_RenderAnnotBitmap / FPDF_FFLDraw pipeline as
+ * SignatureFieldOverlay to produce the button's native PDF appearance.
+ */
+import React, { useEffect, useMemo, useRef, useState, memo } from 'react';
+import { renderButtonFieldAppearances, type SignatureFieldAppearance } from '@app/services/pdfiumService';
+
+interface ButtonAppearanceOverlayProps {
+  pageIndex: number;
+  pdfSource: File | Blob | null;
+  pageWidth: number;
+  pageHeight: number;
+}
+let _cachedSource: File | Blob | null = null;
+let _cachePromise: Promise<SignatureFieldAppearance[]> | null = null;
+
+async function resolveButtonAppearances(source: File | Blob): Promise<SignatureFieldAppearance[]> {
+  if (source === _cachedSource && _cachePromise) return _cachePromise;
+  _cachedSource = source;
+  _cachePromise = source.arrayBuffer().then((buf) => renderButtonFieldAppearances(buf));
+  return _cachePromise;
+}
+function ButtonBitmapCanvas({ imageData, cssWidth, cssHeight }: {
+  imageData: ImageData;
+  cssWidth: number;
+  cssHeight: number;
+}) {
+  const canvasRef = useRef<HTMLCanvasElement>(null);
+
+  useEffect(() => {
+    const canvas = canvasRef.current;
+    if (!canvas) return;
+    canvas.width = imageData.width;
+    canvas.height = imageData.height;
+    const ctx = canvas.getContext('2d');
+    if (ctx) ctx.putImageData(imageData, 0, 0);
+  }, [imageData]);
+
+  return (
+    <canvas
+      ref={canvasRef}
+      style={{ width: cssWidth, height: cssHeight, display: 'block' }}
+    />
+  );
+}
+function ButtonAppearanceOverlayInner({
+  pageIndex,
+  pdfSource,
+  pageWidth,
+  pageHeight,
+}: ButtonAppearanceOverlayProps) {
+  const [appearances, setAppearances] = useState<SignatureFieldAppearance[]>([]);
+
+  useEffect(() => {
+    if (!pdfSource) { setAppearances([]); return; }
+    let cancelled = false;
+    resolveButtonAppearances(pdfSource)
+      .then((res) => { if (!cancelled) setAppearances(res); })
+      .catch(() => { if (!cancelled) setAppearances([]); });
+    return () => { cancelled = true; };
+  }, [pdfSource]);
+
+  const pageAppearances = useMemo(
+    () => appearances.filter((a) => a.pageIndex === pageIndex && a.imageData !== null),
+    [appearances, pageIndex],
+  );
+
+  if (pageAppearances.length === 0) return null;
+
+  return (
+    <div
+      style={{
+        position: 'absolute',
+        top: 0,
+        left: 0,
+        width: '100%',
+        height: '100%',
+        pointerEvents: 'none',
+        zIndex: 4,
+      }}
+      data-button-appearance-page={pageIndex}
+    >
+      {pageAppearances.map((btn, idx) => {
+        const sx = btn.sourcePageWidth  > 0 ? pageWidth  / btn.sourcePageWidth  : 1;
+        const sy = btn.sourcePageHeight > 0 ? pageHeight / btn.sourcePageHeight : 1;
+        const left   = btn.x * sx;
+        const top    = btn.y * sy;
+        const width  = btn.width  * sx;
+        const height = btn.height * sy;
+
+        return (
+          <div
+            key={`btn-appearance-${btn.fieldName}-${idx}`}
+            style={{
+              position: 'absolute',
+              left,
+              top,
+              width,
+              height,
+              overflow: 'hidden',
+            }}
+          >
+            <ButtonBitmapCanvas
+              imageData={btn.imageData!}
+              cssWidth={width}
+              cssHeight={height}
+            />
+          </div>
+        );
+      })}
+    </div>
+  );
+}
+
+export const ButtonAppearanceOverlay = memo(ButtonAppearanceOverlayInner);

frontend/src/core/tools/formFill/FieldInput.tsx

@@ -138,15 +138,13 @@ function FieldInputInner({
     case 'radio': {
       const radioOptions: { value: string; label: string }[] = [];
       if (field.widgets && field.widgets.length > 0) {
-        for (const w of field.widgets) {
-          if (w.exportValue && !radioOptions.some((o) => o.value === w.exportValue)) {
-            radioOptions.push({ value: w.exportValue, label: w.exportValue });
-          }
+        for (let i = 0; i < field.widgets.length; i++) {
+          const w = field.widgets[i];
+          // Use widget index as value; display option label, export value, or index
+          const label = (field.options && field.options[i]) || w.exportValue || String(i);
+          radioOptions.push({ value: String(i), label });
         }
       }
-      if (radioOptions.length === 0 && field.options) {
-        radioOptions.push(...field.options.map((o) => ({ value: o, label: o })));
-      }
       return (
         <Radio.Group
           value={value}

frontend/src/core/tools/formFill/FormFieldOverlay.tsx

@@ -20,7 +20,110 @@
 import React, { useCallback, useMemo, memo } from 'react';
 import { useDocumentState } from '@embedpdf/core/react';
 import { useFormFill, useFieldValue } from '@app/tools/formFill/FormFillContext';
-import type { FormField, WidgetCoordinates } from '@app/tools/formFill/types';
+import { useViewer } from '@app/contexts/ViewerContext';
+import type { FormField, WidgetCoordinates, ButtonAction } from '@app/tools/formFill/types';
+
+/**
+ * Execute PDF JavaScript in a minimally sandboxed context.
+ *
+ * Implements a heuristic security check by statically rejecting scripts containing
+ * common browser globals (`window`, `document`, `fetch`), reflection APIs,
+ * or execution sinks (`eval`, `Function`).
+ *
+ * Valid scripts run in strict mode with dangerous globals explicitly masked
+ * to `undefined`, allowing safe Acrobat APIs like `this.print()` or `app.alert()`.
+ */
+function executePdfJs(
+  js: string,
+  handlers: {
+    print: () => void;
+    save: () => void;
+    submitForm: (url: string) => void;
+    resetForm: () => void;
+  },
+): void {
+  // 1. Static sanitization: Reject scripts with potentially harmful or unneeded keywords.
+  // This blocks most elementary exploits and prevents prototype tampering.
+  const forbidden = [
+    'window', 'document', 'fetch', 'xmlhttprequest', 'websocket', 'worker',
+    'eval', 'settimeout', 'setinterval', 'function', 'constructor',
+    '__proto__', 'prototype', 'globalthis', 'import', 'require'
+  ];
+
+  const lowerJs = js.toLowerCase();
+  for (const word of forbidden) {
+    if (lowerJs.includes(word)) {
+      console.warn(`[PDF JS] Execution blocked: Script contains suspicious keyword "${word}".`, 'Script:', js);
+      return;
+    }
+  }
+
+  // 2. Mock Acrobat API
+  const doOpenUrl = (url: string) => {
+    try {
+      const u = new URL(url);
+      if (['http:', 'https:', 'mailto:'].includes(u.protocol)) {
+        window.open(url, '_blank', 'noopener,noreferrer');
+      }
+    } catch { /* invalid URL — ignore */ }
+  };
+
+  const app = {
+    print: (_params?: unknown) => handlers.print(),
+    alert: (msg: unknown) => { console.debug('[PDF JS] alert:', msg); },
+    beep: () => {},
+    response: () => null,
+    execMenuItem: (item: string) => {
+      switch (item) {
+        case 'Print': handlers.print(); break;
+        case 'Save':  handlers.save();  break;
+        case 'Close': break; // no-op in browser context
+        default: console.debug('[PDF JS] execMenuItem: unhandled item:', item);
+      }
+    },
+    // Prevent prototype walking
+    __proto__: null
+  };
+
+  const doc = {
+    print: (_params?: unknown) => handlers.print(),
+    save: (_params?: unknown) => handlers.save(),
+    saveAs: (_params?: unknown) => handlers.save(),
+    submitForm: (urlOrParams: unknown) => {
+      const url =
+        typeof urlOrParams === 'string'
+          ? urlOrParams
+          : (urlOrParams as Record<string, unknown>)?.cURL as string ?? '';
+      if (url) doOpenUrl(url); else handlers.submitForm(url);
+    },
+    resetForm: (_fields?: unknown) => handlers.resetForm(),
+    getField: (_name: string) => null,
+    getAnnot: () => null,
+    getURL: (url: string) => doOpenUrl(url),
+    numPages: 1,
+    dirty: false,
+  };
+
+  // Stub event object — used by field calculation/validation scripts
+  const event = {
+    value: '',
+    changeEx: '',
+    change: '',
+    rc: true,
+    willCommit: false,
+    target: null as null,
+  };
+
+  try {
+    // Pass doc, app, event as both `this` AND named parameters so scripts that
+    // reference them as free variables (not just via `this`) work correctly.
+    const fn = new Function('app', 'doc', 'event', js);
+    fn.call(doc, app, doc, event);
+  } catch (err) {
+    // Swallow errors from missing PDF APIs; log in debug mode for tracing
+    console.debug('[PDF JS] Script execution error (expected for unsupported APIs):', err, '\nScript:', js.slice(0, 200));
+  }
+}
 
 interface WidgetInputProps {
   field: FormField;
@@ -31,6 +134,7 @@ interface WidgetInputProps {
   scaleY: number;
   onFocus: (fieldName: string) => void;
   onChange: (fieldName: string, value: string) => void;
+  onButtonClick: (field: FormField, action?: ButtonAction | null) => void;
 }
 
 /**
@@ -47,6 +151,7 @@ function WidgetInputInner({
   scaleY,
   onFocus,
   onChange,
+  onButtonClick,
 }: WidgetInputProps) {
   // Per-field value subscription — only this widget re-renders when its value changes
   const value = useFieldValue(field.name);
@@ -287,10 +392,12 @@ function WidgetInputInner({
     }
 
     case 'radio': {
-      // Each radio widget has an exportValue set by the backend
-      const optionValue = widget.exportValue || '';
-      if (!optionValue) return null; // no export value, skip
-      const isSelected = value === optionValue;
+      // Identify this widget by its index within the field's widgets array.
+      // This avoids issues with duplicate exportValues (e.g., all "Yes").
+      const widgetIndex = field.widgets?.indexOf(widget) ?? -1;
+      if (widgetIndex < 0) return null;
+      const widgetIndexStr = String(widgetIndex);
+      const isSelected = value === widgetIndexStr;
       return (
         <div
           {...commonProps}
@@ -304,11 +411,11 @@ function WidgetInputInner({
             paddingLeft: Math.max(1, (height - Math.min(width, height) * 0.8) / 2), // Slight offset
             cursor: field.readOnly ? 'default' : 'pointer',
           }}
-          title={error || field.tooltip || `${field.label}: ${optionValue}`}
+          title={error || field.tooltip || `${field.label}: ${widget.exportValue || widgetIndexStr}`}
           onClick={(e) => {
-            if (field.readOnly || value === optionValue) return; // Don't deselect radio buttons
+            if (field.readOnly || value === widgetIndexStr) return; // Don't deselect radio buttons
             handleFocus();
-            onChange(field.name, optionValue);
+            onChange(field.name, widgetIndexStr);
             stopPropagation(e);
           }}
         >
@@ -317,8 +424,8 @@ function WidgetInputInner({
               width: Math.min(width, height) * 0.8,
               height: Math.min(width, height) * 0.8,
               borderRadius: '50%',
-              border: `1.5px solid ${isSelected || isActive ? '#2196F3' : '#666'}`,
-              background: isSelected ? '#2196F3' : '#FFF',
+              border: `1.5px solid ${isSelected ? '#2196F3' : isActive ? '#2196F3' : '#999'}`,
+              background: isSelected ? '#2196F3' : 'transparent',
               display: 'flex',
               alignItems: 'center',
               justifyContent: 'center',
@@ -331,44 +438,58 @@ function WidgetInputInner({
     }
 
     case 'signature':
-      // Signed signatures have a pre-rendered appearance image; render it.
-      if (field.appearanceDataUrl) {
-        return (
-          <img
-            src={field.appearanceDataUrl}
-            style={{
-              position: 'absolute',
-              left,
-              top,
-              width,
-              height,
-              zIndex: 10,
-              pointerEvents: 'none',
-              userSelect: 'none',
-              display: 'block',
-            }}
-            alt={field.label || 'Signature'}
-            draggable={false}
-          />
-        );
+      // Signature fields are handled entirely by SignatureFieldOverlay (bitmap canvas).
+      // Rendering a placeholder here creates a visible grey overlay on top of the
+      // signature appearance, so we skip it entirely.
+      return null;
+
+    case 'button': {
+      // Transparent hit-target only — visual appearance is rendered by ButtonAppearanceOverlay
+      // (which paints the PDF's native /AP bitmap onto a canvas behind this div).
+      const buttonLabel = field.buttonLabel || field.value || field.label || 'Button';
+      const isClickable = !field.readOnly;
+
+      let actionHint = '';
+      if (field.buttonAction) {
+        switch (field.buttonAction.type) {
+          case 'named': actionHint = field.buttonAction.namedAction ?? ''; break;
+          case 'resetForm': actionHint = 'Reset Form'; break;
+          case 'submitForm': actionHint = `Submit to: ${field.buttonAction.url ?? ''}`.trim(); break;
+          case 'uri': actionHint = field.buttonAction.url ?? ''; break;
+          case 'javascript': actionHint = 'Script'; break;
+        }
       }
-      // Unsigned signature — fall through to placeholder
-      // falls through
-    case 'button':
-      // Just render a highlighted area — not editable
+      const titleText = field.tooltip || (actionHint ? `${buttonLabel} (${actionHint})` : buttonLabel);
+
       return (
         <div
           {...commonProps}
           style={{
             ...commonStyle,
-            background: 'rgba(200,200,200,0.3)',
-            border: '1px dashed #999',
-            cursor: 'default',
+            background: 'transparent',
+            border: 'none',
+            boxShadow: 'none',
+            cursor: isClickable ? 'pointer' : 'default',
+          }}
+          title={titleText}
+          role="button"
+          tabIndex={isClickable ? 0 : -1}
+          aria-label={buttonLabel}
+          onClick={(e) => {
+            handleFocus();
+            if (isClickable) onButtonClick(field, field.buttonAction);
+            stopPropagation(e);
+          }}
+          onKeyDown={(e) => {
+            if (isClickable && (e.key === 'Enter' || e.key === ' ')) {
+              e.preventDefault();
+              onButtonClick(field, field.buttonAction);
+            }
+            stopPropagation(e);
           }}
-          title={field.tooltip || `${field.type}: ${field.label}`}
-          onClick={handleFocus}
         />
       );
+    }
 
     default:
       return (
@@ -407,6 +528,7 @@ export function FormFieldOverlay({
 }: FormFieldOverlayProps) {
   const { setValue, setActiveField, fieldsByPage, state, forFileId } = useFormFill();
   const { activeFieldName, validationErrors } = state;
+  const { printActions, scrollActions, exportActions } = useViewer();
 
   // Get scale from EmbedPDF document state — same pattern as LinkLayer
   // NOTE: All hooks must be called unconditionally (before any early returns)
@@ -416,20 +538,28 @@ export function FormFieldOverlay({
     const pdfPage = documentState?.document?.pages?.[pageIndex];
     if (!pdfPage || !pdfPage.size || !pageWidth || !pageHeight) {
       const s = documentState?.scale ?? 1;
+      if (pageIndex === 0) {
+        console.debug('[FormFieldOverlay] page 0 using fallback scale=%f (missing pdfPage.size)', s);
+      }
       return { scaleX: s, scaleY: s };
     }
 
-    // pdfPage.size contains un-rotated (MediaBox) dimensions;
-    // pageWidth/pageHeight from Scroller also use these un-rotated dims * scale
-    return {
-      scaleX: pageWidth / pdfPage.size.width,
-      scaleY: pageHeight / pdfPage.size.height,
-    };
+    const sx = pageWidth / pdfPage.size.width;
+    const sy = pageHeight / pdfPage.size.height;
+    if (pageIndex === 0) {
+      console.debug(
+        '[FormFieldOverlay] page 0 scale: pageW=%f pageH=%f pdfW=%f pdfH=%f → scaleX=%f scaleY=%f docScale=%f',
+        pageWidth, pageHeight, pdfPage.size.width, pdfPage.size.height, sx, sy, documentState?.scale,
+      );
+    }
+    // pdfPage.size contains un-rotated dimensions from the engine;
+    // pageWidth/pageHeight from Scroller = pdfPage.size * documentScale
+    return { scaleX: sx, scaleY: sy };
   }, [documentState, pageIndex, pageWidth, pageHeight]);
 
   const pageFields = useMemo(
     () => fieldsByPage.get(pageIndex) || [],
-    [fieldsByPage, pageIndex],
+    [fieldsByPage, pageIndex]
   );
 
   const handleFocus = useCallback(
@@ -442,6 +572,64 @@ export function FormFieldOverlay({
     [setValue]
   );
 
+  const handleButtonClick = useCallback(
+    (field: FormField, action?: ButtonAction | null) => {
+      const doOpenUrl = (url: string) => {
+        try {
+          const u = new URL(url);
+          if (['http:', 'https:', 'mailto:'].includes(u.protocol)) {
+            window.open(url, '_blank', 'noopener,noreferrer');
+          }
+        } catch { /* invalid URL */ }
+      };
+      const doResetForm = () => {
+        for (const f of state.fields) setValue(f.name, f.value ?? '');
+      };
+      const doSave = () => { exportActions.saveAsCopy(); };
+
+      if (!action) {
+        // Action extraction failed — fall back to label matching as a last resort
+        const label = (field.buttonLabel || field.label || '').toLowerCase();
+        if (/print/.test(label)) printActions.print();
+        else if (/save|download/.test(label)) doSave();
+        else if (/reset|clear/.test(label)) doResetForm();
+        return;
+      }
+
+      switch (action.type) {
+        case 'named':
+          switch (action.namedAction) {
+            case 'Print': printActions.print(); break;
+            case 'Save': doSave(); break;
+            case 'NextPage': scrollActions.scrollToNextPage(); break;
+            case 'PrevPage': scrollActions.scrollToPreviousPage(); break;
+            case 'FirstPage': scrollActions.scrollToFirstPage(); break;
+            case 'LastPage': scrollActions.scrollToLastPage(); break;
+          }
+          break;
+        case 'resetForm':
+          doResetForm();
+          break;
+        case 'submitForm':
+        case 'uri':
+          if (action.url) doOpenUrl(action.url);
+          break;
+        case 'javascript':
+          // Execute in a sandboxed PDF JS environment instead of just logging
+          if (action.javascript) {
+            executePdfJs(action.javascript, {
+              print: () => printActions.print(),
+              save: doSave,
+              submitForm: doOpenUrl,
+              resetForm: doResetForm,
+            });
+          }
+          break;
+      }
+    },
+    [printActions, scrollActions, exportActions, state.fields, setValue],
+  );
+
   // Guard: don't render fields from a previous document.
   // If fileId is provided and doesn't match what the context fetched for, render nothing.
   if (fileId != null && forFileId != null && fileId !== forFileId) {
@@ -485,6 +673,7 @@ export function FormFieldOverlay({
                 scaleY={scaleY}
                 onFocus={handleFocus}
                 onChange={handleChange}
+                onButtonClick={handleButtonClick}
               />
             );
           })

frontend/src/core/tools/formFill/FormFillContext.tsx

@@ -32,8 +32,9 @@ import React, {
 import { useDebouncedCallback } from '@mantine/hooks';
 import type { FormField, FormFillState, WidgetCoordinates } from '@app/tools/formFill/types';
 import type { IFormDataProvider } from '@app/tools/formFill/providers/types';
-import { PdfLibFormProvider, fetchSignatureFieldsWithAppearances } from '@app/tools/formFill/providers/PdfLibFormProvider';
 import { PdfBoxFormProvider } from '@app/tools/formFill/providers/PdfBoxFormProvider';
+import { PdfiumFormProvider } from '@app/tools/formFill/providers/PdfiumFormProvider';
+import { fetchSignatureFieldsWithAppearances } from '@app/services/pdfiumService';
 
 // ---------------------------------------------------------------------------
 // FormValuesStore — external store for field values (outside React state)
@@ -268,7 +269,7 @@ export function useAllFormValues(): Record<string, string> {
 }
 
 /** Singleton provider instances */
-const pdfLibProvider = new PdfLibFormProvider();
+const pdfiumProvider = new PdfiumFormProvider();
 const pdfBoxProvider = new PdfBoxFormProvider();
 
 export function FormFillProvider({
@@ -283,7 +284,7 @@ export function FormFillProvider({
   const [providerMode, setProviderModeState] = useState<'pdflib' | 'pdfbox'>(initialMode);
   const providerModeRef = useRef(initialMode as 'pdflib' | 'pdfbox');
   providerModeRef.current = providerMode;
-  const provider = providerProp ?? (providerMode === 'pdfbox' ? pdfBoxProvider : pdfLibProvider);
+  const provider = providerProp ?? (providerMode === 'pdfbox' ? pdfBoxProvider : pdfiumProvider);
   const providerRef = useRef(provider);
   providerRef.current = provider;
 
@@ -322,7 +323,7 @@ export function FormFillProvider({
       let fields = await providerRef.current.fetchFields(file);
       // If another fetch or reset happened while we were waiting, discard this result
       if (fetchVersionRef.current !== version) {
-        console.log('[FormFill] Discarding stale fetch result (version mismatch)');
+        console.debug('[FormFill] Discarding stale fetch result (version mismatch)');
         return;
       }
 
@@ -330,7 +331,9 @@ export function FormFillProvider({
       // (they're not fillable). Fetch them via pdflib so their appearances still render.
       if (providerModeRef.current === 'pdfbox') {
         try {
-          const sigFields = await fetchSignatureFieldsWithAppearances(file);
+          // Convert File/Blob to ArrayBuffer for pdfiumService
+          const arrayBuffer = await file.arrayBuffer();
+          const sigFields = await fetchSignatureFieldsWithAppearances(arrayBuffer);
           if (fetchVersionRef.current !== version) return; // stale check after async
           if (sigFields.length > 0) {
             fields = [...fields, ...sigFields];
@@ -420,7 +423,7 @@ export function FormFillProvider({
       if (providerModeRef.current === mode) return;
 
       // provider (pdfbox vs pdflib).
-      const newProvider = mode === 'pdfbox' ? pdfBoxProvider : pdfLibProvider;
+      const newProvider = mode === 'pdfbox' ? pdfBoxProvider : pdfiumProvider;
       providerRef.current = newProvider;
       providerModeRef.current = mode;
 

frontend/src/core/tools/formFill/index.ts

@@ -7,5 +7,5 @@ export { FieldInput } from '@app/tools/formFill/FieldInput';
 export { FIELD_TYPE_ICON, FIELD_TYPE_COLOR } from '@app/tools/formFill/fieldMeta';
 export type { FormField, FormFieldType, FormFillState, WidgetCoordinates } from '@app/tools/formFill/types';
 export type { IFormDataProvider } from '@app/tools/formFill/providers/types';
-export { PdfLibFormProvider } from '@app/tools/formFill/providers/PdfLibFormProvider';
+export { PdfiumFormProvider } from '@app/tools/formFill/providers/PdfiumFormProvider';
 export { PdfBoxFormProvider } from '@app/tools/formFill/providers/PdfBoxFormProvider';

frontend/src/core/tools/formFill/providers/PdfLibFormProvider.ts

@@ -1,865 +0,0 @@
-/**
- * PdfLibFormProvider — Frontend-only form data provider using pdf-lib.
- *
- * Extracts form fields directly from the PDF byte stream and fills them
- * without any backend calls. This avoids sending large PDFs (potentially
- * hundreds of MB) to the server for a feature that can be done entirely
- * on the client.
- *
- * Used in normal viewer mode when the user views a PDF with form fields.
- *
- * Coordinate system:
- * pdf-lib provides widget rectangles in PDF user space (lower-left origin).
- * We transform them to CSS space (top-left origin) matching what the backend
- * FormUtils.createWidgetCoordinates() does, so the same overlay code works
- * for both providers.
- */
-import { PDFDocument, PDFForm, PDFField, PDFTextField, PDFCheckBox,
-  PDFDropdown, PDFRadioGroup, PDFOptionList, PDFButton, PDFSignature,
-  PDFName, PDFDict, PDFArray, PDFNumber, PDFRef, PDFPage,
-  PDFString, PDFHexString, PDFStream } from '@cantoo/pdf-lib';
-import type { PDFDocumentProxy } from 'pdfjs-dist/legacy/build/pdf.mjs';
-import { pdfWorkerManager } from '@app/services/pdfWorkerManager';
-import type { FormField, FormFieldType, WidgetCoordinates } from '@app/tools/formFill/types';
-import type { IFormDataProvider } from '@app/tools/formFill/providers/types';
-
-/**
- * Read a File/Blob as ArrayBuffer.
- */
-async function readAsArrayBuffer(file: File | Blob): Promise<ArrayBuffer> {
-  return file.arrayBuffer();
-}
-
-/**
- * Get the page index for a widget annotation by finding which page contains it.
- */
-function getWidgetPageIndex(
-  widget: PDFDict,
-  pages: PDFPage[],
-): number {
-  // Check /P entry first (direct page reference)
-  const pRef = widget.get(PDFName.of('P'));
-  if (pRef instanceof PDFRef) {
-    for (let i = 0; i < pages.length; i++) {
-      if (pages[i].ref === pRef) return i;
-    }
-  }
-
-  // Fall back to scanning each page's /Annots array
-  const widgetRef = findWidgetRef(widget, pages);
-  if (widgetRef !== undefined) return widgetRef;
-
-  return 0; // default to first page
-}
-
-function findWidgetRef(widget: PDFDict, pages: PDFPage[]): number | undefined {
-  for (let i = 0; i < pages.length; i++) {
-    const annots = pages[i].node.lookup(PDFName.of('Annots'));
-    if (annots instanceof PDFArray) {
-      for (let j = 0; j < annots.size(); j++) {
-        const annotRef = annots.get(j);
-        const annotDict = annots.lookup(j);
-        if (annotDict === widget || annotRef === (widget as any).ref) {
-          return i;
-        }
-      }
-    }
-  }
-  return undefined;
-}
-
-/**
- * Get the page rotation in degrees (0, 90, 180, 270).
- */
-function getPageRotation(page: PDFPage): number {
-  const rot = page.getRotation();
-  return rot?.angle ?? 0;
-}
-
-/**
- * Extract widget rectangles from a PDFField, transforming from PDF space
- * (lower-left origin) to CSS space (top-left origin).
- *
- * Widget /Rect coordinates are always in un-rotated PDF user space
- * (defined by the MediaBox/CropBox). We only need a y-flip to convert
- * from PDF's lower-left origin to CSS's upper-left origin.
- *
- * The embedpdf viewer wraps all page content (including this overlay)
- * inside a <Rotate> CSS component that handles visual rotation.
- * Therefore we must NOT apply any rotation here — doing so would
- * double-rotate the widgets.
- */
-function extractWidgets(
-  field: PDFField,
-  pages: PDFPage[],
-  _doc: PDFDocument,
-): WidgetCoordinates[] {
-  const widgets: WidgetCoordinates[] = [];
-  // Access the underlying PDFDict from the acro field
-  const acroFieldDict = (field.acroField as any).dict as PDFDict;
-
-  // Get all widget annotations for this field
-  const widgetDicts = getFieldWidgets(acroFieldDict);
-
-  for (const wDict of widgetDicts) {
-    const rect = wDict.lookup(PDFName.of('Rect'));
-    if (!(rect instanceof PDFArray) || rect.size() < 4) continue;
-
-    const x1 = numberVal(rect.lookup(0));
-    const y1 = numberVal(rect.lookup(1));
-    const x2 = numberVal(rect.lookup(2));
-    const y2 = numberVal(rect.lookup(3));
-
-    const pageIndex = getWidgetPageIndex(wDict, pages);
-    const page = pages[pageIndex];
-    if (!page) continue;
-
-    // Get CropBox dimensions (un-rotated) for coordinate transformation
-    const cropBox = getCropBox(page);
-    const cropHeight = cropBox.height;
-    const cropX = cropBox.x;
-    const cropY = cropBox.y;
-
-    // Widget rect in PDF space (lower-left origin, un-rotated)
-    const pdfX = Math.min(x1, x2);
-    const pdfY = Math.min(y1, y2);
-    const pdfW = Math.abs(x2 - x1);
-    const pdfH = Math.abs(y2 - y1);
-
-    // Adjust relative to CropBox origin
-    const relativeX = pdfX - cropX;
-    const relativeY = pdfY - cropY;
-
-    // Convert from PDF lower-left origin to CSS upper-left origin (y-flip).
-    // No rotation transform here — the <Rotate> CSS component in the viewer
-    // handles page rotation for all overlays including form fields.
-    const finalX = relativeX;
-    const finalY = cropHeight - relativeY - pdfH;
-    const finalW = pdfW;
-    const finalH = pdfH;
-
-    // Extract export value for checkboxes/radios
-    let exportValue: string | undefined;
-    const ap = wDict.lookup(PDFName.of('AP'));
-    if (ap instanceof PDFDict) {
-      const normal = ap.lookup(PDFName.of('N'));
-      if (normal instanceof PDFDict) {
-        // The keys of /N (other than /Off) are the export values.
-        // PDFDict.entries() reliably returns [PDFName, PDFObject][] in
-        // @cantoo/pdf-lib — no optional chaining needed.
-        try {
-          const entries = normal.entries();
-          const keys = entries
-            .map(([k]) => k.decodeText())
-            .filter((k) => k !== 'Off');
-          if (keys.length > 0) exportValue = keys[0];
-        } catch {
-          // Malformed AP dict — skip export value extraction
-        }
-      }
-    }
-    // Also check /AS for current appearance state
-    if (!exportValue) {
-      const asEntry = wDict.lookup(PDFName.of('AS'));
-      if (asEntry instanceof PDFName) {
-        const asVal = asEntry.decodeText();
-        if (asVal !== 'Off') exportValue = asVal;
-      }
-    }
-
-    // Extract font size from default appearance string
-    let fontSize: number | undefined;
-    const da = wDict.lookup(PDFName.of('DA'));
-    if (da) {
-      const daStr = da.toString();
-      const tfMatch = daStr.match(/(\d+(?:\.\d+)?)\s+Tf/);
-      if (tfMatch) {
-        fontSize = parseFloat(tfMatch[1]);
-        if (fontSize === 0) fontSize = undefined; // 0 means auto-size
-      }
-    }
-
-    widgets.push({
-      pageIndex,
-      x: finalX,
-      y: finalY,
-      width: finalW,
-      height: finalH,
-      exportValue,
-      fontSize,
-    });
-  }
-
-  return widgets;
-}
-
-function numberVal(obj: any): number {
-  if (obj instanceof PDFNumber) return obj.asNumber();
-  if (typeof obj === 'number') return obj;
-  return 0;
-}
-
-/**
- * Get the CropBox (or MediaBox fallback) dimensions in un-rotated PDF space.
- * These are the raw dictionary values without any rotation adjustment.
- */
-function getCropBox(page: PDFPage): { x: number; y: number; width: number; height: number } {
-  // Check direct CropBox entry
-  const cropBox = page.node.lookup(PDFName.of('CropBox'));
-  if (cropBox instanceof PDFArray && cropBox.size() >= 4) {
-    return {
-      x: numberVal(cropBox.lookup(0)),
-      y: numberVal(cropBox.lookup(1)),
-      width: numberVal(cropBox.lookup(2)) - numberVal(cropBox.lookup(0)),
-      height: numberVal(cropBox.lookup(3)) - numberVal(cropBox.lookup(1)),
-    };
-  }
-  // Check direct MediaBox entry
-  const mediaBox = page.node.lookup(PDFName.of('MediaBox'));
-  if (mediaBox instanceof PDFArray && mediaBox.size() >= 4) {
-    return {
-      x: numberVal(mediaBox.lookup(0)),
-      y: numberVal(mediaBox.lookup(1)),
-      width: numberVal(mediaBox.lookup(2)) - numberVal(mediaBox.lookup(0)),
-      height: numberVal(mediaBox.lookup(3)) - numberVal(mediaBox.lookup(1)),
-    };
-  }
-  // Traverse parent page-tree nodes for inherited MediaBox
-  let node: any = page.node;
-  while (node) {
-    const parentNode = node.lookup(PDFName.of('Parent'));
-    if (parentNode instanceof PDFDict) {
-      const inheritedBox = parentNode.lookup(PDFName.of('MediaBox'));
-      if (inheritedBox instanceof PDFArray && inheritedBox.size() >= 4) {
-        return {
-          x: numberVal(inheritedBox.lookup(0)),
-          y: numberVal(inheritedBox.lookup(1)),
-          width: numberVal(inheritedBox.lookup(2)) - numberVal(inheritedBox.lookup(0)),
-          height: numberVal(inheritedBox.lookup(3)) - numberVal(inheritedBox.lookup(1)),
-        };
-      }
-      node = parentNode;
-    } else {
-      break;
-    }
-  }
-  // Last resort: use page.getSize() but un-rotate the dimensions
-  const { width, height } = page.getSize();
-  const rotation = getPageRotation(page);
-  if (rotation === 90 || rotation === 270) {
-    return { x: 0, y: 0, width: height, height: width };
-  }
-  return { x: 0, y: 0, width, height };
-}
-
-/**
- * Get the widget annotation dictionaries for a field.
- * A field can either BE a widget (merged) or have child /Kids that are widgets.
- */
-function getFieldWidgets(acroField: PDFDict): PDFDict[] {
-  const kids = acroField.lookup(PDFName.of('Kids'));
-  if (kids instanceof PDFArray) {
-    const result: PDFDict[] = [];
-    for (let i = 0; i < kids.size(); i++) {
-      const kid = kids.lookup(i);
-      if (kid instanceof PDFDict) {
-        // Check if this kid is a widget (has /Rect) vs another field node
-        const subtype = kid.lookup(PDFName.of('Subtype'));
-        if (subtype instanceof PDFName && subtype.decodeText() === 'Widget') {
-          result.push(kid);
-        } else if (kid.lookup(PDFName.of('Rect'))) {
-          // Merged field/widget — has Rect but maybe no explicit Subtype
-          result.push(kid);
-        } else {
-          // Intermediate field node — recurse
-          result.push(...getFieldWidgets(kid));
-        }
-      }
-    }
-    return result;
-  }
-
-  // No Kids — the field dict itself is the widget (merged field/widget)
-  if (acroField.lookup(PDFName.of('Rect'))) {
-    return [acroField];
-  }
-  return [];
-}
-
-/**
- * Determine the FormFieldType from a pdf-lib PDFField.
- */
-function getFieldType(field: PDFField): FormFieldType {
-  if (field instanceof PDFTextField) return 'text';
-  if (field instanceof PDFCheckBox) return 'checkbox';
-  if (field instanceof PDFDropdown) return 'combobox';
-  if (field instanceof PDFRadioGroup) return 'radio';
-  if (field instanceof PDFOptionList) return 'listbox';
-  if (field instanceof PDFButton) return 'button';
-  if (field instanceof PDFSignature) return 'signature';
-  return 'text';
-}
-
-/**
- * Get the current value of a field as a string.
- */
-function getFieldValue(field: PDFField): string {
-  try {
-    if (field instanceof PDFTextField) {
-      return field.getText() ?? '';
-    }
-    if (field instanceof PDFCheckBox) {
-      return field.isChecked() ? 'Yes' : 'Off';
-    }
-    if (field instanceof PDFDropdown) {
-      const selected = field.getSelected();
-      return selected.length > 0 ? selected[0] : '';
-    }
-    if (field instanceof PDFRadioGroup) {
-      return getRadioValue(field);
-    }
-    if (field instanceof PDFOptionList) {
-      const selected = field.getSelected();
-      return selected.join(',');
-    }
-  } catch {
-    // Some fields may throw on getValue if malformed
-  }
-  return '';
-}
-
-function getRadioValue(field: PDFRadioGroup): string {
-  const selected = field.getSelected() ?? '';
-  if (!selected || selected === 'Off') return selected;
-
-  const options = field.getOptions();
-
-  if (options.includes(selected)) return selected;
-
-  const mappedOption = mapAppearanceStateToOption(field, selected, options);
-  if (mappedOption) return mappedOption;
-
-  const index = parseInt(selected, 10);
-  if (!isNaN(index) && index >= 0 && index < options.length) {
-    return options[index];
-  }
-
-  return selected;
-}
-
-function mapAppearanceStateToOption(
-  field: PDFRadioGroup,
-  stateName: string,
-  options: string[],
-): string | undefined {
-  try {
-    const acroFieldDict = (field.acroField as any).dict as PDFDict;
-    const widgets = getFieldWidgets(acroFieldDict);
-
-    for (let i = 0; i < widgets.length; i++) {
-      const ap = widgets[i].lookup(PDFName.of('AP'));
-      if (!(ap instanceof PDFDict)) continue;
-
-      const normal = ap.lookup(PDFName.of('N'));
-      if (!(normal instanceof PDFDict)) continue;
-
-      let keys: string[] = [];
-      try {
-        keys = normal.entries().map(([k]) => k.decodeText());
-      } catch {
-        continue;
-      }
-      if (keys.includes(stateName) && i < options.length) {
-        return options[i];
-      }
-    }
-  } catch {
-    // Fallback handled by caller
-  }
-  return undefined;
-}
-
-function resolveRadioValueForSelect(
-  field: PDFRadioGroup,
-  value: string,
-): string | null {
-  const options = field.getOptions();
-
-  if (options.includes(value)) return value;
-
-  const mappedOption = mapAppearanceStateToOption(field, value, options);
-  if (mappedOption) return mappedOption;
-
-  const index = parseInt(value, 10);
-  if (!isNaN(index) && index >= 0 && index < options.length) {
-    return options[index];
-  }
-
-  const lower = value.toLowerCase();
-  const match = options.find((o: string) => o.toLowerCase() === lower);
-  if (match) return match;
-
-  return null;
-}
-
-/**
- * Get field options (for dropdowns, listboxes, radios).
- */
-function getFieldOptions(field: PDFField): string[] | null {
-  try {
-    if (field instanceof PDFDropdown) {
-      return field.getOptions();
-    }
-    if (field instanceof PDFOptionList) {
-      return field.getOptions();
-    }
-    if (field instanceof PDFRadioGroup) {
-      return field.getOptions();
-    }
-  } catch {
-    // ignore
-  }
-  return null;
-}
-
-/**
- * Extract display labels from the /Opt array if it contains [export, display]
- * pairs.  PDF spec §12.7.4.4: each element of /Opt may be either a text
- * string (export value == display value) or a two-element array where the
- * first element is the export value and the second is the display text.
- *
- * Returns null when every display value equals its export value (no distinct
- * display labels exist), keeping the interface lean for the common case.
- */
-function getFieldDisplayOptions(field: PDFField): string[] | null {
-  if (!(field instanceof PDFDropdown) && !(field instanceof PDFOptionList)) {
-    return null;
-  }
-
-  try {
-    const acroDict = (field.acroField as any).dict as PDFDict;
-    const optRaw = acroDict.lookup(PDFName.of('Opt'));
-    if (!(optRaw instanceof PDFArray)) return null;
-
-    const displays: string[] = [];
-    let hasDifference = false;
-
-    for (let i = 0; i < optRaw.size(); i++) {
-      try {
-        const entry = optRaw.lookup(i);
-
-        if (entry instanceof PDFArray && entry.size() >= 2) {
-          // [exportValue, displayValue] pair
-          const exp = decodeText(entry.lookup(0));
-          const disp = decodeText(entry.lookup(1));
-          displays.push(disp);
-          if (exp !== disp) hasDifference = true;
-        } else {
-          // Plain string — export and display are the same
-          const val = decodeText(entry);
-          displays.push(val);
-        }
-      } catch {
-        // Malformed /Opt entry — skip but continue processing remaining entries
-        continue;
-      }
-    }
-
-    if (displays.length === 0) return null;
-    return hasDifference ? displays : null;
-  } catch {
-    return null;
-  }
-}
-
-/** Decode a PDFString, PDFHexString, or PDFName to a JS string. */
-function decodeText(obj: unknown): string {
-  if (obj instanceof PDFString || obj instanceof PDFHexString) {
-    return obj.decodeText();
-  }
-  if (obj instanceof PDFName) {
-    return obj.decodeText();
-  }
-  if (typeof obj === 'string') return obj;
-  return String(obj ?? '');
-}
-
-/**
- * Check if a field is read-only.
- */
-function isFieldReadOnly(field: PDFField): boolean {
-  try {
-    return field.isReadOnly();
-  } catch {
-    return false;
-  }
-}
-
-/**
- * Check if a field is required.
- */
-function isFieldRequired(field: PDFField): boolean {
-  try {
-    return field.isRequired();
-  } catch {
-    return false;
-  }
-}
-
-/**
- * Get field tooltip (TU entry).
- * Uses proper PDFString/PDFHexString decoding for correct Unicode support.
- */
-function getFieldTooltip(acroField: PDFDict): string | null {
-  const tu = acroField.lookup(PDFName.of('TU'));
-  if (!tu) return null;
-
-  try {
-    // Prefer decodeText() for proper Unicode handling (UTF-16BE / PDFDocEncoding)
-    if (tu instanceof PDFString || tu instanceof PDFHexString) {
-      return tu.decodeText();
-    }
-    // Fallback: strip parentheses from raw toString() for other object types
-    return tu.toString().replace(/^\(|\)$/g, '');
-  } catch {
-    return null;
-  }
-}
-
-/**
- * Check if a text field is multiline (flag bit 13 set in /Ff).
- */
-function isMultiline(field: PDFField): boolean {
-  if (!(field instanceof PDFTextField)) return false;
-  try {
-    return field.isMultiline();
-  } catch {
-    return false;
-  }
-}
-
-/**
- * Get the label for a field — use the partial name or the full qualified name.
- */
-function getFieldLabel(field: PDFField): string {
-  const name = field.getName();
-  // Use the last segment of the qualified name as the label
-  const parts = name.split('.');
-  return parts[parts.length - 1] || name;
-}
-
-/**
- * Extracts only signed signature fields (those with an /AP/N stream) from a PDF,
- * renders their appearances via PDF.js, and returns them as FormField objects.
- *
- * Used by FormFillContext to inject signature overlays when the pdfbox provider
- * is active (fill form tool), where the backend doesn't return signature fields.
- */
-export async function fetchSignatureFieldsWithAppearances(file: File | Blob): Promise<FormField[]> {
-  const arrayBuffer = await readAsArrayBuffer(file);
-  let doc: PDFDocument;
-  try {
-    doc = await PDFDocument.load(arrayBuffer, {
-      ignoreEncryption: true,
-      updateMetadata: false,
-      throwOnInvalidObject: false,
-    });
-  } catch { return []; }
-
-  let form: PDFForm;
-  try { form = doc.getForm(); } catch { return []; }
-
-  let pdfFields: PDFField[];
-  try { pdfFields = form.getFields(); } catch { return []; }
-
-  let pages: PDFPage[];
-  try { pages = doc.getPages(); } catch { return []; }
-
-  const result: FormField[] = [];
-
-  for (const field of pdfFields) {
-    if (!(field instanceof PDFSignature)) continue;
-    if (!signatureHasAppearance(field)) continue;
-
-    const widgets = extractWidgets(field, pages, doc);
-    if (widgets.length === 0) continue;
-
-    result.push({
-      name: field.getName(),
-      label: getFieldLabel(field),
-      type: 'signature',
-      value: '',
-      options: null,
-      displayOptions: null,
-      required: false,
-      readOnly: true,
-      multiSelect: false,
-      multiline: false,
-      tooltip: getFieldTooltip((field.acroField as any).dict as PDFDict),
-      widgets,
-    });
-  }
-
-  if (result.length > 0) {
-    await attachSignatureAppearances(result, arrayBuffer);
-  }
-
-  return result;
-}
-
-/**
- * Returns true if the signature field has at least one widget with a normal
- * (/AP/N) appearance stream — i.e. the signature has actually been signed.
- */
-function signatureHasAppearance(field: PDFField): boolean {
-  if (!(field instanceof PDFSignature)) return false;
-  try {
-    const acroDict = (field.acroField as any).dict as PDFDict;
-    const widgets = getFieldWidgets(acroDict);
-    for (const wDict of widgets) {
-      const ap = wDict.lookup(PDFName.of('AP'));
-      if (ap instanceof PDFDict) {
-        const n = ap.lookup(PDFName.of('N'));
-        if (n instanceof PDFStream) return true;
-      }
-    }
-  } catch { /* ignore malformed fields */ }
-  return false;
-}
-
-/**
- * For each signature FormField that has an /AP/N stream, renders the
- * containing page via PDF.js and crops out the widget rectangle,
- * attaching the result as field.appearanceDataUrl.
- *
- * Uses the existing pdfWorkerManager for proper worker lifecycle management.
- */
-async function attachSignatureAppearances(
-  signatureFields: FormField[],
-  arrayBuffer: ArrayBuffer,
-): Promise<void> {
-  if (signatureFields.length === 0) return;
-
-  let pdfDoc: PDFDocumentProxy | null = null;
-  try {
-    // Slice so pdf-lib's retained references to the original buffer are unaffected
-    pdfDoc = await pdfWorkerManager.createDocument(arrayBuffer.slice(0));
-
-    // Group fields by the pageIndex of their first widget
-    const byPage = new Map<number, FormField[]>();
-    for (const field of signatureFields) {
-      for (const w of field.widgets ?? []) {
-        const arr = byPage.get(w.pageIndex) ?? [];
-        arr.push(field);
-        byPage.set(w.pageIndex, arr);
-        break; // first widget identifies the page
-      }
-    }
-
-    const RENDER_SCALE = 2; // 2× for crisp appearance
-
-    for (const [pageIndex, fields] of byPage) {
-      const page = await pdfDoc.getPage(pageIndex + 1); // PDF.js is 1-indexed
-      const viewport = page.getViewport({ scale: RENDER_SCALE });
-
-      const canvas = document.createElement('canvas');
-      canvas.width = viewport.width;
-      canvas.height = viewport.height;
-
-      await page.render({ canvas, viewport }).promise;
-
-      for (const field of fields) {
-        for (const widget of field.widgets ?? []) {
-          if (widget.pageIndex !== pageIndex) continue;
-
-          // widget.x/y are PDF points, CSS upper-left origin (relative to CropBox).
-          // PDF.js renders the CropBox starting at canvas (0,0), so multiplying by
-          // RENDER_SCALE gives the correct canvas pixel coordinates for the crop.
-          const cx = Math.round(widget.x * RENDER_SCALE);
-          const cy = Math.round(widget.y * RENDER_SCALE);
-          const cw = Math.max(1, Math.round(widget.width * RENDER_SCALE));
-          const ch = Math.max(1, Math.round(widget.height * RENDER_SCALE));
-
-          const crop = document.createElement('canvas');
-          crop.width = cw;
-          crop.height = ch;
-          const cropCtx = crop.getContext('2d');
-          if (!cropCtx) continue;
-
-          cropCtx.drawImage(canvas, cx, cy, cw, ch, 0, 0, cw, ch);
-          field.appearanceDataUrl = crop.toDataURL('image/png');
-          break; // first widget is representative
-        }
-      }
-
-      page.cleanup();
-    }
-  } catch (e) {
-    console.warn('[PdfLibFormProvider] Failed to extract signature appearances:', e);
-  } finally {
-    if (pdfDoc) pdfWorkerManager.destroyDocument(pdfDoc);
-  }
-}
-
-export class PdfLibFormProvider implements IFormDataProvider {
-  readonly name = 'pdf-lib';
-
-  async fetchFields(file: File | Blob): Promise<FormField[]> {
-    const arrayBuffer = await readAsArrayBuffer(file);
-    let doc: PDFDocument;
-    try {
-      doc = await PDFDocument.load(arrayBuffer, {
-        ignoreEncryption: true,
-        updateMetadata: false,
-        throwOnInvalidObject: false,
-      });
-    } catch (loadError) {
-      console.warn('[PdfLibFormProvider] Failed to load PDF document:', loadError);
-      return [];
-    }
-
-    let form: PDFForm;
-    try {
-      form = doc.getForm();
-    } catch (formError) {
-      // No AcroForm or broken catalog — return empty
-      console.warn('[PdfLibFormProvider] Failed to access AcroForm:', formError);
-      return [];
-    }
-
-    let fields: PDFField[];
-    try {
-      fields = form.getFields();
-    } catch (fieldsError) {
-      console.warn('[PdfLibFormProvider] Failed to enumerate form fields:', fieldsError);
-      return [];
-    }
-    if (fields.length === 0) return [];
-
-    let pages: PDFPage[];
-    try {
-      pages = doc.getPages();
-    } catch (pagesError) {
-      // Pages tree is invalid (same issue as usePdfLibLinks "invalid catalog").
-      // Without page references we can't place widgets, so return empty.
-      // The viewer will fall back to native form rendering via withForms.
-      console.warn(
-        '[PdfLibFormProvider] PDF pages tree is invalid — cannot place form widgets.',
-        'Native form rendering will be used as fallback.',
-        pagesError,
-      );
-      return [];
-    }
-
-    const result: FormField[] = [];
-
-    for (const field of fields) {
-      const fieldName = field.getName();
-      try {
-        const type = getFieldType(field);
-        const widgets = extractWidgets(field, pages, doc);
-
-        // Skip fields with no visible widgets
-        if (widgets.length === 0) continue;
-
-        const formField: FormField = {
-          name: field.getName(),
-          label: getFieldLabel(field),
-          type,
-          value: getFieldValue(field),
-          options: getFieldOptions(field),
-          displayOptions: getFieldDisplayOptions(field),
-          required: isFieldRequired(field),
-          readOnly: isFieldReadOnly(field),
-          multiSelect: field instanceof PDFOptionList,
-          multiline: isMultiline(field),
-          tooltip: getFieldTooltip((field.acroField as any).dict as PDFDict),
-          widgets,
-        };
-
-        result.push(formField);
-      } catch (fieldError) {
-        // Skip individual malformed fields but continue processing
-        console.warn(`[PdfLibFormProvider] Skipping field "${fieldName}":`, fieldError);
-      }
-    }
-
-    // Render appearance streams for signed signature fields so the overlay
-    // can display them as images instead of placeholder boxes.
-    const sigFieldsWithAp = result.filter(
-      f => f.type === 'signature' && signatureHasAppearance(form.getField(f.name)),
-    );
-    if (sigFieldsWithAp.length > 0) {
-      await attachSignatureAppearances(sigFieldsWithAp, arrayBuffer);
-    }
-
-    return result;
-  }
-
-  async fillForm(
-    file: File | Blob,
-    values: Record<string, string>,
-    flatten: boolean,
-  ): Promise<Blob> {
-    const arrayBuffer = await readAsArrayBuffer(file);
-    const doc = await PDFDocument.load(arrayBuffer, {
-      ignoreEncryption: true,
-      throwOnInvalidObject: false,
-    });
-
-    const form = doc.getForm();
-    const fields = form.getFields();
-
-    for (const field of fields) {
-      const fieldName = field.getName();
-      if (!(fieldName in values)) continue;
-
-      const value = values[fieldName];
-
-      try {
-        if (field instanceof PDFTextField) {
-          field.setText(value || undefined);
-        } else if (field instanceof PDFCheckBox) {
-          if (value && value !== 'Off') {
-            field.check();
-          } else {
-            field.uncheck();
-          }
-        } else if (field instanceof PDFDropdown) {
-          if (value) {
-            field.select(value);
-          } else {
-            field.clear();
-          }
-        } else if (field instanceof PDFRadioGroup) {
-          if (value && value !== 'Off') {
-            const resolved = resolveRadioValueForSelect(field, value);
-            if (resolved) {
-              field.select(resolved);
-            } else {
-              console.warn(
-                `[PdfLibFormProvider] Radio value "${value}" could not be mapped to options [${field.getOptions().join(', ')}] for field "${fieldName}"`,
-              );
-            }
-          }
-        } else if (field instanceof PDFOptionList) {
-          if (value) {
-            const vals = value.split(',').filter(Boolean);
-            field.select(vals[0]); // PDFOptionList.select takes single value
-          } else {
-            field.clear();
-          }
-        }
-      } catch (err) {
-        console.warn(`[PdfLibFormProvider] Failed to set value for field "${fieldName}":`, err);
-      }
-    }
-
-    if (flatten) {
-      form.flatten();
-    }
-
-    const pdfBytes = await doc.save();
-    return new Blob([pdfBytes.slice().buffer as ArrayBuffer], { type: 'application/pdf' });
-  }
-}

frontend/src/core/tools/formFill/providers/PdfiumFormProvider.ts

@@ -0,0 +1,599 @@
+/**
+ * PdfiumFormProvider Frontend-only form data provider using PDFium WASM.
+ *
+ * Replaces the old pdf-lib based PdfLibFormProvider.  Extracts form fields
+ * directly from the PDF byte stream via @embedpdf/pdfium WASM and fills
+ * them without any backend calls.
+ *
+ * Used in normal viewer mode when the user views a PDF with form fields.
+ *
+ * Coordinate system:
+ * PDFium provides widget rectangles in PDF user space (lower-left origin).
+ * We transform them to CSS space (top-left origin) matching what the backend
+ * FormUtils.createWidgetCoordinates() does, so the same overlay code works
+ * for both providers.
+ */
+import { PDF_FORM_FIELD_TYPE } from '@app/services/pdfiumService';
+import { FPDF_ANNOT_WIDGET, FLAT_PRINT } from '@app/utils/pdfiumBitmapUtils';
+import type { FormField, FormFieldType, WidgetCoordinates, ButtonAction } from '@app/tools/formFill/types';
+import type { IFormDataProvider } from '@app/tools/formFill/providers/types';
+import {
+  closeDocAndFreeBuffer,
+  extractFormFields,
+  getPdfiumModule,
+  openRawDocumentSafe,
+  readUtf16,
+  saveRawDocument,
+  type PdfiumFormField,
+} from '@app/services/pdfiumService';
+
+/**
+ * Map PDFium form field type enum to our FormFieldType string.
+ */
+function mapFieldType(t: PDF_FORM_FIELD_TYPE): FormFieldType {
+  switch (t) {
+    case PDF_FORM_FIELD_TYPE.TEXTFIELD:
+      return 'text';
+    case PDF_FORM_FIELD_TYPE.CHECKBOX:
+      return 'checkbox';
+    case PDF_FORM_FIELD_TYPE.COMBOBOX:
+      return 'combobox';
+    case PDF_FORM_FIELD_TYPE.RADIOBUTTON:
+      return 'radio';
+    case PDF_FORM_FIELD_TYPE.LISTBOX:
+      return 'listbox';
+    case PDF_FORM_FIELD_TYPE.PUSHBUTTON:
+      return 'button';
+    case PDF_FORM_FIELD_TYPE.SIGNATURE:
+      return 'signature';
+    default:
+      return 'text';
+  }
+}
+
+/**
+ * Convert a PdfiumFormField (from pdfiumService) to the UI FormField shape.
+ * @param optInfo      When provided, overrides options/displayOptions for combo/listbox fields.
+ * @param buttonInfo   When provided, sets buttonLabel and buttonAction for push buttons.
+ */
+function toFormField(
+  f: PdfiumFormField & { _tooltip?: string | null },
+  optInfo?: { exportValues: string[]; displayValues: string[] } | null,
+  buttonInfo?: { label?: string; action?: ButtonAction } | null,
+): FormField {
+  const type = mapFieldType(f.type);
+  const optionLabels = f.options.map((o) => o.label);
+
+  // Build WidgetCoordinates from the PDFium widget rects
+  const widgets: WidgetCoordinates[] = f.widgets.map((w) => ({
+    pageIndex: w.pageIndex,
+    x: w.x,
+    y: w.y,
+    width: w.width,
+    height: w.height,
+    exportValue: w.exportValue,
+    fontSize: w.fontSize,
+  }));
+
+  // Derive value string
+  let value = f.value;
+  if (type === 'checkbox') {
+    value = f.isChecked ? 'Yes' : 'Off';
+  } else if (type === 'radio') {
+    // Use widget index as the canonical radio value.
+    // This avoids issues with duplicate exportValues across widgets
+    // (e.g., all widgets having exportValue "Yes").
+    value = '';
+    for (let i = 0; i < f.widgets.length; i++) {
+      if (f.widgets[i].isChecked) {
+        value = String(i);
+        break;
+      }
+    }
+  }
+
+  // Use pdf-lib extracted export/display values when available
+  let options: string[] | null = optionLabels.length > 0 ? optionLabels : null;
+  let displayOptions: string[] | null = null;
+  if (optInfo && optInfo.exportValues.length > 0) {
+    options = optInfo.exportValues;
+    displayOptions = optInfo.displayValues;
+  }
+
+  return {
+    name: f.name,
+    label: f.name.split('.').pop() || f.name,
+    type,
+    value,
+    options,
+    displayOptions,
+    required: f.isRequired,
+    readOnly: f.isReadOnly,
+    multiSelect: f.type === PDF_FORM_FIELD_TYPE.LISTBOX,
+    multiline: type === 'text' && (f.flags & 0x1000) !== 0,   // bit 13 = Multiline
+    tooltip: f._tooltip ?? null,
+    widgets,
+    buttonLabel: buttonInfo?.label ?? null,
+    buttonAction: buttonInfo?.action ?? null,
+  };
+}
+
+/**
+ * PdfLibFormProvider — now backed by PDFium WASM.
+ *
+ * The class name is kept for backwards-compatibility with existing imports.
+ * Internally everything goes through @embedpdf/pdfium.
+ */
+export class PdfiumFormProvider implements IFormDataProvider {
+  /** Provider identifier — kept as 'pdf-lib' for backwards-compatibility. */
+  readonly name = 'pdf-lib';
+
+  async fetchFields(file: File | Blob): Promise<FormField[]> {
+    try {
+      const arrayBuffer = await file.arrayBuffer();
+      const pdfiumFields = await extractFormFields(arrayBuffer);
+
+      // Enrich with alternate names (tooltips)
+      await this.enrichWithAlternateNames(arrayBuffer, pdfiumFields);
+
+      // Enrich combo/listbox fields with export/display values from pdf-lib
+      const optMap = await this.extractDisplayOptions(arrayBuffer, pdfiumFields);
+
+      // Enrich push buttons with label (/MK/CA) and action (/A) from pdf-lib
+      const buttonInfoMap = await this.extractButtonInfo(arrayBuffer, pdfiumFields);
+
+      return pdfiumFields
+        .filter((f) => f.widgets.length > 0)
+        .map((f) => toFormField(f, optMap.get(f.name) ?? null, buttonInfoMap.get(f.name) ?? null));
+    } catch (err) {
+      console.warn('[PdfiumFormProvider] Failed to extract form fields:', err);
+      return [];
+    }
+  }
+
+  /**
+   * Enrich fields with alternate names (tooltip / TU entry) via PDFium.
+   */
+  private async enrichWithAlternateNames(
+    data: ArrayBuffer,
+    fields: PdfiumFormField[],
+  ): Promise<void> {
+    try {
+      const m = await getPdfiumModule();
+      const docPtr = await openRawDocumentSafe(data);
+      try {
+        const formInfoPtr = m.PDFiumExt_OpenFormFillInfo();
+        const formEnvPtr = m.PDFiumExt_InitFormFillEnvironment(docPtr, formInfoPtr);
+        if (!formEnvPtr) return;
+
+        const pageCount = m.FPDF_GetPageCount(docPtr);
+        const nameToField = new Map(fields.map((f) => [f.name, f]));
+        const enriched = new Set<string>();
+
+        for (let pageIdx = 0; pageIdx < pageCount && enriched.size < nameToField.size; pageIdx++) {
+          const pagePtr = m.FPDF_LoadPage(docPtr, pageIdx);
+          if (!pagePtr) continue;
+          m.FORM_OnAfterLoadPage(pagePtr, formEnvPtr);
+
+          const annotCount = m.FPDFPage_GetAnnotCount(pagePtr);
+          for (let ai = 0; ai < annotCount && enriched.size < nameToField.size; ai++) {
+            const annotPtr = m.FPDFPage_GetAnnot(pagePtr, ai);
+            if (!annotPtr) continue;
+            if (m.FPDFAnnot_GetSubtype(annotPtr) !== FPDF_ANNOT_WIDGET) {
+              m.FPDFPage_CloseAnnot(annotPtr);
+              continue;
+            }
+
+            const nl = m.FPDFAnnot_GetFormFieldName(formEnvPtr, annotPtr, 0, 0);
+            let name = '';
+            if (nl > 0) {
+              const nb = m.pdfium.wasmExports.malloc(nl);
+              m.FPDFAnnot_GetFormFieldName(formEnvPtr, annotPtr, nb, nl);
+              name = readUtf16(m, nb, nl);
+              m.pdfium.wasmExports.free(nb);
+            }
+
+            if (name && nameToField.has(name) && !enriched.has(name)) {
+              const altLen = m.FPDFAnnot_GetFormFieldAlternateName(formEnvPtr, annotPtr, 0, 0);
+              if (altLen > 0) {
+                const altBuf = m.pdfium.wasmExports.malloc(altLen);
+                m.FPDFAnnot_GetFormFieldAlternateName(formEnvPtr, annotPtr, altBuf, altLen);
+                const altName = readUtf16(m, altBuf, altLen);
+                m.pdfium.wasmExports.free(altBuf);
+                (nameToField.get(name) as any)._tooltip = altName || null;
+              }
+              enriched.add(name);
+            }
+
+            m.FPDFPage_CloseAnnot(annotPtr);
+          }
+
+          m.FORM_OnBeforeClosePage(pagePtr, formEnvPtr);
+          m.FPDF_ClosePage(pagePtr);
+        }
+
+        m.PDFiumExt_ExitFormFillEnvironment(formEnvPtr);
+        m.PDFiumExt_CloseFormFillInfo(formInfoPtr);
+      } finally {
+        closeDocAndFreeBuffer(m, docPtr);
+      }
+    } catch (e) {
+      console.warn('[PdfiumFormProvider] Failed to enrich alternate names:', e);
+    }
+  }
+
+  /**
+   * Use pdf-lib to read /Opt arrays for combo/listbox fields.
+   * Returns a map of fieldName → { exportValues, displayValues }.
+   * PDFium only exposes display labels; pdf-lib can read the raw /Opt entries
+   * to separate [export, display] pairs.
+   */
+  private async extractDisplayOptions(
+    data: ArrayBuffer,
+    fields: PdfiumFormField[],
+  ): Promise<Map<string, { exportValues: string[]; displayValues: string[] }>> {
+    const result = new Map<string, { exportValues: string[]; displayValues: string[] }>();
+    const comboOrList = fields.filter(
+      (f) => f.type === PDF_FORM_FIELD_TYPE.COMBOBOX || f.type === PDF_FORM_FIELD_TYPE.LISTBOX,
+    );
+    if (comboOrList.length === 0) return result;
+
+    try {
+      const { PDFDocument, PDFName, PDFArray, PDFString, PDFHexString, PDFDropdown, PDFOptionList } =
+        await import('@cantoo/pdf-lib');
+      const doc = await PDFDocument.load(data, { ignoreEncryption: true, throwOnInvalidObject: false });
+      const form = doc.getForm();
+
+      const decodeText = (obj: unknown): string => {
+        if (obj instanceof PDFString || obj instanceof PDFHexString) return obj.decodeText();
+        return String(obj ?? '');
+      };
+
+      for (const pf of comboOrList) {
+        try {
+          const field = form.getField(pf.name);
+          if (!(field instanceof PDFDropdown) && !(field instanceof PDFOptionList)) continue;
+
+          const acroDict = (field.acroField as any).dict;
+          const optRaw = acroDict.lookup(PDFName.of('Opt'));
+          if (!(optRaw instanceof PDFArray)) continue;
+
+          const exportValues: string[] = [];
+          const displayValues: string[] = [];
+          let hasDifference = false;
+
+          for (let i = 0; i < optRaw.size(); i++) {
+            try {
+              const entry = optRaw.lookup(i);
+              if (entry instanceof PDFArray && entry.size() >= 2) {
+                const exp = decodeText(entry.lookup(0));
+                const disp = decodeText(entry.lookup(1));
+                exportValues.push(exp);
+                displayValues.push(disp);
+                if (exp !== disp) hasDifference = true;
+              } else {
+                const val = decodeText(entry);
+                exportValues.push(val);
+                displayValues.push(val);
+              }
+            } catch {
+              continue;
+            }
+          }
+
+          if (exportValues.length > 0) {
+            result.set(pf.name, {
+              exportValues,
+              displayValues: hasDifference ? displayValues : exportValues,
+            });
+          }
+        } catch {
+          // Skip individual field errors
+        }
+      }
+    } catch (e) {
+      console.warn('[PdfiumFormProvider] Failed to extract display options:', e);
+    }
+
+    return result;
+  }
+
+  /**
+   * Use pdf-lib to extract push button labels (/MK/CA) and actions (/A) for each button field.
+   * Returns a map of fieldName → { label?, action? }.
+   */
+  private async extractButtonInfo(
+    data: ArrayBuffer,
+    fields: PdfiumFormField[],
+  ): Promise<Map<string, { label?: string; action?: ButtonAction }>> {
+    const result = new Map<string, { label?: string; action?: ButtonAction }>();
+    const buttons = fields.filter((f) => f.type === PDF_FORM_FIELD_TYPE.PUSHBUTTON);
+    if (buttons.length === 0) return result;
+
+    try {
+      const { PDFDocument, PDFName, PDFString, PDFHexString, PDFDict } =
+        await import('@cantoo/pdf-lib');
+
+      const doc = await PDFDocument.load(data, { ignoreEncryption: true, throwOnInvalidObject: false });
+      const form = doc.getForm();
+
+      const decodeText = (obj: unknown): string | null => {
+        if (obj instanceof PDFString || obj instanceof PDFHexString) return obj.decodeText();
+        if (obj instanceof PDFName) return (obj as any).asString?.() ?? obj.toString().replace(/^\//, '');
+        return null;
+      };
+
+      const parseActionDict = (aObj: unknown): ButtonAction | null => {
+        if (!(aObj instanceof PDFDict)) return null;
+        const sObj = aObj.lookup(PDFName.of('S'));
+        if (!(sObj instanceof PDFName)) return null;
+        const actionType: string = (sObj as any).asString?.() ?? sObj.toString().replace(/^\//, '');
+
+        switch (actionType) {
+          case 'Named': {
+            const nObj = aObj.lookup(PDFName.of('N'));
+            const name = nObj instanceof PDFName
+              ? ((nObj as any).asString?.() ?? nObj.toString().replace(/^\//, ''))
+              : '';
+            return { type: 'named', namedAction: name };
+          }
+          case 'JavaScript': {
+            const jsObj = aObj.lookup(PDFName.of('JS'));
+            const js = decodeText(jsObj) ?? jsObj?.toString() ?? '';
+            return { type: 'javascript', javascript: js };
+          }
+          case 'SubmitForm': {
+            const fObj = aObj.lookup(PDFName.of('F'));
+            let url = '';
+            if (fObj instanceof PDFDict) {
+              url = decodeText(fObj.lookup(PDFName.of('F'))) ?? '';
+            } else if (fObj) {
+              url = decodeText(fObj) ?? fObj.toString();
+            }
+            const flagsObj = aObj.lookup(PDFName.of('Flags'));
+            const flags = typeof (flagsObj as any)?.asNumber === 'function' ? (flagsObj as any).asNumber() : 0;
+            return { type: 'submitForm', url, submitFlags: flags };
+          }
+          case 'ResetForm':
+            return { type: 'resetForm' };
+          case 'URI': {
+            const uriObj = aObj.lookup(PDFName.of('URI'));
+            return { type: 'uri', url: decodeText(uriObj) ?? '' };
+          }
+          default:
+            return null;
+        }
+      };
+
+      const getMkCaption = (dict: any): string | null => {
+        try {
+          const mkObj = dict.lookup(PDFName.of('MK'));
+          if (!(mkObj instanceof PDFDict)) return null;
+          const caObj = mkObj.lookup(PDFName.of('CA'));
+          return decodeText(caObj);
+        } catch {
+          return null;
+        }
+      };
+
+      const getActionFromDict = (dict: any): ButtonAction | null => {
+        try {
+          return parseActionDict(dict.lookup(PDFName.of('A')));
+        } catch {
+          return null;
+        }
+      };
+
+      const buttonNames = new Set(buttons.map((b) => b.name));
+
+      for (const field of form.getFields()) {
+        const name = field.getName();
+        if (!buttonNames.has(name)) continue;
+
+        try {
+          const acroField = (field as any).acroField;
+          if (!acroField?.dict) continue;
+
+          const info: { label?: string; action?: ButtonAction } = {};
+
+          // Try widget dicts first (each widget can have its own /MK and /A)
+          const widgets: any[] = (acroField as any).getWidgets?.() ?? [];
+          for (const widget of widgets) {
+            if (!info.label) {
+              const label = getMkCaption(widget.dict);
+              if (label) info.label = label;
+            }
+            if (!info.action) {
+              const action = getActionFromDict(widget.dict);
+              if (action) info.action = action;
+            }
+            if (info.label && info.action) break;
+          }
+
+          // Fall back to field-level dict
+          if (!info.label) {
+            const label = getMkCaption(acroField.dict);
+            if (label) info.label = label;
+          }
+          if (!info.action) {
+            const action = getActionFromDict(acroField.dict);
+            if (action) info.action = action;
+          }
+
+          // Also check /AA (Additional Actions) → /U (Mouse Up) if no /A found
+          if (!info.action) {
+            try {
+              const aaObj = acroField.dict.lookup(PDFName.of('AA'));
+              if (aaObj instanceof PDFDict) {
+                const uObj = aaObj.lookup(PDFName.of('U'));
+                const action = parseActionDict(uObj);
+                if (action) info.action = action;
+              }
+            } catch { /* non-critical */ }
+          }
+
+          if (info.label || info.action) {
+            result.set(name, info);
+          }
+        } catch { /* skip individual field errors */ }
+      }
+    } catch (e) {
+      console.warn('[PdfiumFormProvider] Failed to extract button info:', e);
+    }
+
+    return result;
+  }
+
+  async fillForm(
+    file: File | Blob,
+    values: Record<string, string>,
+    flatten: boolean,
+  ): Promise<Blob> {
+    const arrayBuffer = await file.arrayBuffer();
+    const m = await getPdfiumModule();
+    const docPtr = await openRawDocumentSafe(arrayBuffer);
+
+    try {
+      const formInfoPtr = m.PDFiumExt_OpenFormFillInfo();
+      const formEnvPtr = m.PDFiumExt_InitFormFillEnvironment(docPtr, formInfoPtr);
+      if (!formEnvPtr) {
+        throw new Error('PDFium: failed to initialise form environment');
+      }
+
+      const pageCount = m.FPDF_GetPageCount(docPtr);
+
+      // Track radio widget index per field for index-based matching.
+      // The UI stores radio values as widget indices (e.g., "0", "1", "2").
+      const radioWidgetIdx = new Map<string, number>();
+
+      for (let pageIdx = 0; pageIdx < pageCount; pageIdx++) {
+        const pagePtr = m.FPDF_LoadPage(docPtr, pageIdx);
+        if (!pagePtr) continue;
+        m.FORM_OnAfterLoadPage(pagePtr, formEnvPtr);
+
+        const annotCount = m.FPDFPage_GetAnnotCount(pagePtr);
+        for (let ai = 0; ai < annotCount; ai++) {
+          const annotPtr = m.FPDFPage_GetAnnot(pagePtr, ai);
+          if (!annotPtr) continue;
+          if (m.FPDFAnnot_GetSubtype(annotPtr) !== FPDF_ANNOT_WIDGET) {
+            m.FPDFPage_CloseAnnot(annotPtr);
+            continue;
+          }
+
+          const nl = m.FPDFAnnot_GetFormFieldName(formEnvPtr, annotPtr, 0, 0);
+          let fieldName = '';
+          if (nl > 0) {
+            const nb = m.pdfium.wasmExports.malloc(nl);
+            m.FPDFAnnot_GetFormFieldName(formEnvPtr, annotPtr, nb, nl);
+            fieldName = readUtf16(m, nb, nl);
+            m.pdfium.wasmExports.free(nb);
+          }
+
+          if (!fieldName || !(fieldName in values)) {
+            m.FPDFPage_CloseAnnot(annotPtr);
+            continue;
+          }
+
+          const value = values[fieldName];
+          const fieldType = m.FPDFAnnot_GetFormFieldType(formEnvPtr, annotPtr);
+
+          try {
+            if (fieldType === PDF_FORM_FIELD_TYPE.TEXTFIELD) {
+              m.FORM_SetFocusedAnnot(formEnvPtr, annotPtr);
+              m.FORM_SelectAllText(formEnvPtr, pagePtr);
+              const wPtr = m.pdfium.wasmExports.malloc((value.length + 1) * 2);
+              m.pdfium.stringToUTF16(value, wPtr, (value.length + 1) * 2);
+              m.FORM_ReplaceSelection(formEnvPtr, pagePtr, wPtr);
+              m.pdfium.wasmExports.free(wPtr);
+              m.FORM_ForceToKillFocus(formEnvPtr);
+            } else if (fieldType === PDF_FORM_FIELD_TYPE.CHECKBOX) {
+              // Toggle checkbox using the same approach as @embedpdf engine:
+              // Focus → Enter key (FORM_OnChar with keycode 13) → Kill focus.
+              // Click simulation (FORM_OnLButtonDown/Up) does NOT reliably
+              // persist checkbox state changes in headless/offscreen mode.
+              const isCurrentlyChecked = m.FPDFAnnot_IsChecked(formEnvPtr, annotPtr);
+              const shouldBeChecked = value !== '' && value !== 'Off';
+              if (isCurrentlyChecked !== shouldBeChecked) {
+                const ENTER_KEY = 13;
+                m.FORM_SetFocusedAnnot(formEnvPtr, annotPtr);
+                m.FORM_OnChar(formEnvPtr, pagePtr, ENTER_KEY, 0);
+                m.FORM_ForceToKillFocus(formEnvPtr);
+              }
+            } else if (fieldType === PDF_FORM_FIELD_TYPE.RADIOBUTTON) {
+              // Radio values are stored as widget indices (e.g., "0", "1", "2").
+              // Track the current widget index for this field and toggle only
+              // the widget whose index matches the stored value.
+              const currentIdx = radioWidgetIdx.get(fieldName) ?? 0;
+              radioWidgetIdx.set(fieldName, currentIdx + 1);
+
+              const targetIdx = parseInt(value, 10);
+              if (!isNaN(targetIdx) && currentIdx === targetIdx) {
+                const isAlreadyChecked = m.FPDFAnnot_IsChecked(formEnvPtr, annotPtr);
+                if (!isAlreadyChecked) {
+                  const ENTER_KEY = 13;
+                  m.FORM_SetFocusedAnnot(formEnvPtr, annotPtr);
+                  m.FORM_OnChar(formEnvPtr, pagePtr, ENTER_KEY, 0);
+                  m.FORM_ForceToKillFocus(formEnvPtr);
+                }
+              }
+            } else if (
+              fieldType === PDF_FORM_FIELD_TYPE.COMBOBOX ||
+              fieldType === PDF_FORM_FIELD_TYPE.LISTBOX
+            ) {
+              // FORM_SetIndexSelected requires the annotation to be focused first.
+              m.FORM_SetFocusedAnnot(formEnvPtr, annotPtr);
+
+              let matched = false;
+              const optCount = m.FPDFAnnot_GetOptionCount(formEnvPtr, annotPtr);
+              for (let oi = 0; oi < optCount; oi++) {
+                const optLen = m.FPDFAnnot_GetOptionLabel(formEnvPtr, annotPtr, oi, 0, 0);
+                if (optLen > 0) {
+                  const ob = m.pdfium.wasmExports.malloc(optLen);
+                  m.FPDFAnnot_GetOptionLabel(formEnvPtr, annotPtr, oi, ob, optLen);
+                  const optLabel = readUtf16(m, ob, optLen);
+                  m.pdfium.wasmExports.free(ob);
+                  if (optLabel === value) {
+                    m.FORM_SetIndexSelected(formEnvPtr, pagePtr, oi, true);
+                    matched = true;
+                    break;
+                  }
+                }
+              }
+
+              // Fallback: set as text (handles editable combos or
+              // cases where export values differ from display labels).
+              if (!matched && value) {
+                m.FORM_SelectAllText(formEnvPtr, pagePtr);
+                const wPtr = m.pdfium.wasmExports.malloc((value.length + 1) * 2);
+                m.pdfium.stringToUTF16(value, wPtr, (value.length + 1) * 2);
+                m.FORM_ReplaceSelection(formEnvPtr, pagePtr, wPtr);
+                m.pdfium.wasmExports.free(wPtr);
+              }
+
+              m.FORM_ForceToKillFocus(formEnvPtr);
+            }
+          } catch (err) {
+            console.warn(`[PdfiumFormProvider] Failed to set "${fieldName}":`, err);
+          }
+
+          m.FPDFPage_CloseAnnot(annotPtr);
+        }
+
+        if (flatten) {
+          m.FPDFPage_Flatten(pagePtr, FLAT_PRINT);
+        }
+
+        m.FORM_OnBeforeClosePage(pagePtr, formEnvPtr);
+        m.FPDF_ClosePage(pagePtr);
+      }
+
+      m.PDFiumExt_ExitFormFillEnvironment(formEnvPtr);
+      m.PDFiumExt_CloseFormFillInfo(formInfoPtr);
+
+      const savedBytes = await saveRawDocument(docPtr);
+      return new Blob([savedBytes], { type: 'application/pdf' });
+    } finally {
+      closeDocAndFreeBuffer(m, docPtr);
+    }
+  }
+}

frontend/src/core/tools/formFill/providers/index.ts

@@ -1,3 +1,3 @@
 export type { IFormDataProvider } from '@app/tools/formFill/providers/types';
-export { PdfLibFormProvider } from '@app/tools/formFill/providers/PdfLibFormProvider';
+export { PdfiumFormProvider } from '@app/tools/formFill/providers/PdfiumFormProvider';
 export { PdfBoxFormProvider } from '@app/tools/formFill/providers/PdfBoxFormProvider';

frontend/src/core/tools/formFill/types.ts

@@ -30,6 +30,10 @@ export interface FormField {
   multiline: boolean;
   tooltip: string | null;
   widgets: WidgetCoordinates[] | null;
+  /** Visual label for push buttons (from /MK/CA in the PDF appearance dict) */
+  buttonLabel?: string | null;
+  /** Action descriptor for push buttons */
+  buttonAction?: ButtonAction | null;
   /** Pre-rendered appearance image for signed signature fields (data URL). */
   appearanceDataUrl?: string;
 }
@@ -43,6 +47,26 @@ export type FormFieldType =
   | 'button'
   | 'signature';
 
+export type ButtonActionType =
+  | 'named'
+  | 'javascript'
+  | 'submitForm'
+  | 'resetForm'
+  | 'uri'
+  | 'none';
+
+export interface ButtonAction {
+  type: ButtonActionType;
+  /** For 'named' actions: the PDF action name (e.g. 'Print', 'NextPage', 'PrevPage') */
+  namedAction?: string;
+  /** For 'javascript' actions: the JavaScript source code */
+  javascript?: string;
+  /** For 'submitForm' / 'uri' actions: the target URL */
+  url?: string;
+  /** For 'submitForm' actions: submit flags bitmask */
+  submitFlags?: number;
+}
+
 export interface FormFillState {
   /** Fields fetched from backend with coordinates */
   fields: FormField[];

frontend/src/core/utils/imageToPdfUtils.ts

@@ -1,4 +1,8 @@
-import { PDFDocument, PageSizes } from '@cantoo/pdf-lib';
+import {
+  getPdfiumModule,
+  saveRawDocument,
+} from '@app/services/pdfiumService';
+import { copyRgbaToBgraHeap } from '@app/utils/pdfiumBitmapUtils';
 
 export interface ImageToPdfOptions {
   imageResolution?: 'full' | 'reduced';
@@ -6,11 +10,14 @@ export interface ImageToPdfOptions {
   stretchToFit?: boolean;
 }
 
+// Standard page sizes in PDF points (72 dpi)
+const PAGE_SIZES = {
+  A4: [595.276, 841.890] as [number, number],
+  Letter: [612, 792] as [number, number],
+};
+
 /**
- * Convert an image file to a PDF file
- * @param imageFile - The image file to convert (JPEG, PNG, etc.)
- * @param options - Conversion options
- * @returns A Promise that resolves to a PDF File object
+ * Convert an image file to a PDF file using PDFium WASM.
  */
 export async function convertImageToPdf(
   imageFile: File,
@@ -21,121 +28,143 @@ export async function convertImageToPdf(
     pageFormat = 'A4',
     stretchToFit = false,
   } = options;
-  try {
-    // Create a new PDF document
-    const pdfDoc = await PDFDocument.create();
 
-    // Read the image file as an array buffer
-    let imageBytes = await imageFile.arrayBuffer();
+  try {
+    const m = await getPdfiumModule();
+
+    // Read the image file
+    let imageBlob: Blob = imageFile;
 
     // Apply image resolution reduction if requested
     if (imageResolution === 'reduced') {
-      const reducedImage = await reduceImageResolution(imageFile, 1200); // Max 1200px on longest side
-      imageBytes = await reducedImage.arrayBuffer();
+      imageBlob = await reduceImageResolution(imageFile, 1200);
     }
 
-    // Embed the image based on its type
-    let image;
-    const imageType = imageFile.type.toLowerCase();
-
-    if (imageType === 'image/jpeg' || imageType === 'image/jpg') {
-      image = await pdfDoc.embedJpg(imageBytes);
-    } else if (imageType === 'image/png') {
-      image = await pdfDoc.embedPng(imageBytes);
-    } else {
-      // For other image types, try to convert to PNG first using canvas
-      const convertedImage = await convertImageToPng(imageFile);
-      const convertedBytes = await convertedImage.arrayBuffer();
-      image = await pdfDoc.embedPng(convertedBytes);
+    // Decode image to RGBA pixels via canvas
+    const decoded = await decodeImageToRgba(imageBlob);
+    if (!decoded) {
+      throw new Error('Failed to decode image');
     }
 
-    // Get image dimensions
-    const { width: imageWidth, height: imageHeight } = image;
+    const { rgba, width: imageWidth, height: imageHeight } = decoded;
 
-    // Determine page dimensions based on pageFormat option
+    // Determine page dimensions
     let pageWidth: number;
     let pageHeight: number;
 
     if (pageFormat === 'keep') {
-      // Use original image dimensions
       pageWidth = imageWidth;
       pageHeight = imageHeight;
     } else if (pageFormat === 'letter') {
-      // US Letter: 8.5" x 11" = 612 x 792 points
-      pageWidth = PageSizes.Letter[0];
-      pageHeight = PageSizes.Letter[1];
+      [pageWidth, pageHeight] = PAGE_SIZES.Letter;
     } else {
-      // A4: 210mm x 297mm = 595 x 842 points (default)
-      pageWidth = PageSizes.A4[0];
-      pageHeight = PageSizes.A4[1];
+      [pageWidth, pageHeight] = PAGE_SIZES.A4;
     }
 
-    // Adjust page orientation based on image orientation if using standard page size
+    // Adjust orientation to match image
     if (pageFormat !== 'keep') {
       const imageIsLandscape = imageWidth > imageHeight;
       const pageIsLandscape = pageWidth > pageHeight;
-
-      // Rotate page to match image orientation
       if (imageIsLandscape !== pageIsLandscape) {
         [pageWidth, pageHeight] = [pageHeight, pageWidth];
       }
     }
 
-    // Create a page
-    const page = pdfDoc.addPage([pageWidth, pageHeight]);
-
-    // Calculate image placement based on stretchToFit option
+    // Calculate image placement
     let drawX: number;
     let drawY: number;
     let drawWidth: number;
     let drawHeight: number;
 
     if (stretchToFit || pageFormat === 'keep') {
-      // Stretch/fill to page
       drawX = 0;
       drawY = 0;
       drawWidth = pageWidth;
       drawHeight = pageHeight;
     } else {
-      // Fit within page bounds while preserving aspect ratio
       const imageAspectRatio = imageWidth / imageHeight;
       const pageAspectRatio = pageWidth / pageHeight;
 
       if (imageAspectRatio > pageAspectRatio) {
-        // Image is wider than page - fit to width
         drawWidth = pageWidth;
         drawHeight = pageWidth / imageAspectRatio;
         drawX = 0;
-        drawY = (pageHeight - drawHeight) / 2; // Center vertically
+        drawY = (pageHeight - drawHeight) / 2;
       } else {
-        // Image is taller than page - fit to height
         drawHeight = pageHeight;
         drawWidth = pageHeight * imageAspectRatio;
         drawY = 0;
-        drawX = (pageWidth - drawWidth) / 2; // Center horizontally
+        drawX = (pageWidth - drawWidth) / 2;
       }
     }
 
-    // Draw the image on the page
-    page.drawImage(image, {
-      x: drawX,
-      y: drawY,
-      width: drawWidth,
-      height: drawHeight,
-    });
+    // Create new PDF document
+    const docPtr = m.FPDF_CreateNewDocument();
+    if (!docPtr) throw new Error('PDFium: failed to create document');
 
-    // Save the PDF to bytes
-    const pdfBytes = await pdfDoc.save();
+    try {
+      // Create a page
+      const pagePtr = m.FPDFPage_New(docPtr, 0, pageWidth, pageHeight);
+      if (!pagePtr) throw new Error('PDFium: failed to create page');
 
-    // Create a filename by replacing the image extension with .pdf
-    const pdfFilename = imageFile.name.replace(/\.[^.]+$/, '.pdf');
+      // Create bitmap from RGBA data (PDFium uses BGRA)
+      const bitmapPtr = m.FPDFBitmap_Create(imageWidth, imageHeight, 1);
+      if (!bitmapPtr) throw new Error('PDFium: failed to create bitmap');
 
-    // Create a File object from the PDF bytes
-    const pdfFile = new File([new Uint8Array(pdfBytes)], pdfFilename, {
-      type: 'application/pdf',
-    });
+      const bufferPtr = m.FPDFBitmap_GetBuffer(bitmapPtr);
+      const stride = m.FPDFBitmap_GetStride(bitmapPtr);
 
-    return pdfFile;
+      // Bulk RGBA → BGRA copy via shared utility
+      copyRgbaToBgraHeap(m, rgba, bufferPtr, imageWidth, imageHeight, stride);
+
+      // Create image page object
+      const imageObjPtr = m.FPDFPageObj_NewImageObj(docPtr);
+      if (!imageObjPtr) {
+        m.FPDFBitmap_Destroy(bitmapPtr);
+        throw new Error('PDFium: failed to create image object');
+      }
+
+      const setBitmapOk = m.FPDFImageObj_SetBitmap(pagePtr, 0, imageObjPtr, bitmapPtr);
+      m.FPDFBitmap_Destroy(bitmapPtr);
+
+      if (!setBitmapOk) {
+        m.FPDFPageObj_Destroy(imageObjPtr);
+        throw new Error('PDFium: failed to set bitmap on image object');
+      }
+
+      // Set transformation matrix: scale + translate
+      // FS_MATRIX: {a, b, c, d, e, f} — 6 floats
+      const matrixPtr = m.pdfium.wasmExports.malloc(6 * 4);
+      m.pdfium.setValue(matrixPtr, drawWidth, 'float');       // a = scaleX
+      m.pdfium.setValue(matrixPtr + 4, 0, 'float');           // b
+      m.pdfium.setValue(matrixPtr + 8, 0, 'float');           // c
+      m.pdfium.setValue(matrixPtr + 12, drawHeight, 'float'); // d = scaleY
+      m.pdfium.setValue(matrixPtr + 16, drawX, 'float');      // e = translateX
+      m.pdfium.setValue(matrixPtr + 20, drawY, 'float');      // f = translateY
+
+      const setMatrixOk = m.FPDFPageObj_SetMatrix(imageObjPtr, matrixPtr);
+      m.pdfium.wasmExports.free(matrixPtr);
+
+      if (!setMatrixOk) {
+        m.FPDFPageObj_Destroy(imageObjPtr);
+        throw new Error('PDFium: failed to set image matrix');
+      }
+
+      // Insert image into page
+      m.FPDFPage_InsertObject(pagePtr, imageObjPtr);
+
+      // Generate page content stream
+      m.FPDFPage_GenerateContent(pagePtr);
+      m.FPDF_ClosePage(pagePtr);
+
+      // Save document
+      const pdfBytes = await saveRawDocument(docPtr);
+      const pdfFilename = imageFile.name.replace(/\.[^.]+$/, '.pdf');
+
+      return new File([pdfBytes], pdfFilename, { type: 'application/pdf' });
+    } finally {
+      m.FPDF_CloseDocument(docPtr);
+    }
   } catch (error) {
     console.error('Error converting image to PDF:', error);
     throw new Error(
@@ -146,57 +175,41 @@ export async function convertImageToPdf(
 }
 
 /**
- * Convert an image file to PNG using canvas
- * This is used for image types that pdf-lib doesn't directly support
+ * Decode an image Blob to RGBA pixel data via canvas.
  */
-async function convertImageToPng(imageFile: File): Promise<File> {
-  return new Promise((resolve, reject) => {
+function decodeImageToRgba(imageBlob: Blob): Promise<{ rgba: Uint8Array; width: number; height: number } | null> {
+  return new Promise((resolve) => {
     const img = new Image();
-    const url = URL.createObjectURL(imageFile);
+    const url = URL.createObjectURL(imageBlob);
 
     img.onload = () => {
       try {
-        // Create a canvas with the image dimensions
         const canvas = document.createElement('canvas');
         canvas.width = img.width;
         canvas.height = img.height;
-
-        // Draw the image on the canvas
         const ctx = canvas.getContext('2d');
         if (!ctx) {
-          throw new Error('Failed to get canvas context');
+          URL.revokeObjectURL(url);
+          resolve(null);
+          return;
         }
         ctx.drawImage(img, 0, 0);
-
-        // Convert canvas to blob
-        canvas.toBlob(
-          (blob) => {
-            if (!blob) {
-              reject(new Error('Failed to convert canvas to blob'));
-              return;
-            }
-
-            // Create a File object from the blob
-            const pngFilename = imageFile.name.replace(/\.[^.]+$/, '.png');
-            const pngFile = new File([blob], pngFilename, {
-              type: 'image/png',
-            });
-
-            URL.revokeObjectURL(url);
-            resolve(pngFile);
-          },
-          'image/png',
-          1.0
-        );
-      } catch (error) {
+        const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
         URL.revokeObjectURL(url);
-        reject(error);
+        resolve({
+          rgba: new Uint8Array(imageData.data.buffer),
+          width: canvas.width,
+          height: canvas.height,
+        });
+      } catch {
+        URL.revokeObjectURL(url);
+        resolve(null);
       }
     };
 
     img.onerror = () => {
       URL.revokeObjectURL(url);
-      reject(new Error('Failed to load image'));
+      resolve(null);
     };
 
     img.src = url;
@@ -205,9 +218,6 @@ async function convertImageToPng(imageFile: File): Promise<File> {
 
 /**
  * Reduce image resolution to a maximum dimension
- * @param imageFile - The image file to reduce
- * @param maxDimension - Maximum width or height in pixels
- * @returns A Promise that resolves to a reduced resolution image file
  */
 async function reduceImageResolution(
   imageFile: File,
@@ -221,14 +231,12 @@ async function reduceImageResolution(
       try {
         const { width, height } = img;
 
-        // Check if reduction is needed
         if (width <= maxDimension && height <= maxDimension) {
           URL.revokeObjectURL(url);
-          resolve(imageFile); // No reduction needed
+          resolve(imageFile);
           return;
         }
 
-        // Calculate new dimensions while preserving aspect ratio
         let newWidth: number;
         let newHeight: number;
 
@@ -240,19 +248,14 @@ async function reduceImageResolution(
           newWidth = (width / height) * maxDimension;
         }
 
-        // Create a canvas with the new dimensions
         const canvas = document.createElement('canvas');
         canvas.width = newWidth;
         canvas.height = newHeight;
 
-        // Draw the resized image on the canvas
         const ctx = canvas.getContext('2d');
-        if (!ctx) {
-          throw new Error('Failed to get canvas context');
-        }
+        if (!ctx) throw new Error('Failed to get canvas context');
         ctx.drawImage(img, 0, 0, newWidth, newHeight);
 
-        // Convert canvas to blob (preserve original format if possible)
         const outputType = imageFile.type.startsWith('image/')
           ? imageFile.type
           : 'image/jpeg';
@@ -263,17 +266,12 @@ async function reduceImageResolution(
               reject(new Error('Failed to convert canvas to blob'));
               return;
             }
-
-            // Create a File object from the blob
-            const reducedFile = new File([blob], imageFile.name, {
-              type: outputType,
-            });
-
+            const reducedFile = new File([blob], imageFile.name, { type: outputType });
             URL.revokeObjectURL(url);
             resolve(reducedFile);
           },
           outputType,
-          0.9 // Quality (only applies to JPEG)
+          0.9,
         );
       } catch (error) {
         URL.revokeObjectURL(url);

frontend/src/core/utils/pdfLinkUtils.ts

@@ -1,18 +1,24 @@
 /**
  * pdfLinkUtils — Create, modify, and extract link annotations in PDF documents.
+ *
+ * Migrated from @cantoo/pdf-lib to @embedpdf/pdfium WASM.
+ * All operations are performed via PDFium C API wrappers.
  */
 import {
-  PDFDocument,
-  PDFPage,
-  PDFName,
-  PDFString,
-  PDFArray,
-  PDFDict,
-  PDFRef,
-  PDFContext,
-  PDFNumber,
-  PDFHexString,
-} from '@cantoo/pdf-lib';
+  getPdfiumModule,
+  openRawDocumentSafe,
+  closeDocAndFreeBuffer,
+  saveRawDocument,
+  readUtf16,
+  writeUtf16,
+  readAnnotRectAdjusted,
+  parseRectToCss,
+} from '@app/services/pdfiumService';
+import {
+  FPDF_ANNOT_LINK,
+  PDFACTION_GOTO,
+  PDFACTION_URI,
+} from '@app/utils/pdfiumBitmapUtils';
 
 export type LinkType = 'internal' | 'external' | 'unknown';
 export type LinkBorderStyle = 'solid' | 'dashed' | 'beveled' | 'inset' | 'underline';
@@ -40,9 +46,9 @@ export interface PdfLibLink {
 }
 
 export interface CreateLinkOptions {
-  /** Page to place the link on. */
-  page: PDFPage;
-  /** Link rectangle in PDF user-space coordinates (lower-left origin). */
+  /** 0-based page index. */
+  pageIndex: number;
+  /** Link rectangle in CSS (top-left origin) coordinate space. */
   rect: { x: number; y: number; width: number; height: number };
   /** External URL (mutually exclusive with destinationPage). */
   url?: string;
@@ -62,22 +68,21 @@ export interface CreateLinkOptions {
 
 /**
  * Create a link annotation on a PDF page.
- * Supports both external URIs and internal GoTo page destinations.
+ * Mutates the document in-place and returns the updated PDF bytes.
  */
-export function createLinkAnnotation(
-  pdfDoc: PDFDocument,
+export async function createLinkAnnotation(
+  data: ArrayBuffer | Uint8Array,
   options: CreateLinkOptions,
-): void {
+  password?: string,
+): Promise<ArrayBuffer> {
   const {
-    page,
+    pageIndex,
     rect,
     url,
     destinationPage,
     title,
     color = [0, 0, 1],
     borderWidth = 0,
-    borderStyle = 'solid',
-    highlightMode = 'invert',
   } = options;
 
   if (!url && destinationPage === undefined) {
@@ -86,468 +91,244 @@ export function createLinkAnnotation(
   if (url && destinationPage !== undefined) {
     throw new Error('createLinkAnnotation: url and destinationPage are mutually exclusive');
   }
-  if (destinationPage !== undefined) {
-    const pageCount = pdfDoc.getPageCount();
-    if (destinationPage < 0 || destinationPage >= pageCount) {
+  if (rect.width <= 0 || rect.height <= 0) {
+    throw new Error('createLinkAnnotation: rect dimensions must be positive');
+  }
+
+  const m = await getPdfiumModule();
+  const docPtr = await openRawDocumentSafe(data, password);
+
+  try {
+    const pageCount = m.FPDF_GetPageCount(docPtr);
+    if (destinationPage !== undefined && (destinationPage < 0 || destinationPage >= pageCount)) {
       throw new RangeError(
         `createLinkAnnotation: destinationPage ${destinationPage} out of range [0, ${pageCount})`,
       );
     }
-  }
-  if (rect.width <= 0 || rect.height <= 0) {
-    throw new Error('createLinkAnnotation: rect dimensions must be positive');
-  }
-  if (color.some((c) => c < 0 || c > 1)) {
-    throw new RangeError('createLinkAnnotation: color components must be between 0 and 1');
-  }
-  if (borderWidth < 0) {
-    throw new RangeError('createLinkAnnotation: borderWidth must be non-negative');
-  }
 
-  const ctx = pdfDoc.context;
+    const pagePtr = m.FPDF_LoadPage(docPtr, pageIndex);
+    if (!pagePtr) throw new Error(`Failed to load page ${pageIndex}`);
 
-  const entries: Record<string, any> = {
-    Type: 'Annot',
-    Subtype: 'Link',
-    Rect: [rect.x, rect.y, rect.x + rect.width, rect.y + rect.height],
-    Border: [0, 0, borderWidth],
-    C: color,
-    H: PDFName.of(highlightModeCode(highlightMode)),
-  };
+    try {
+      const pageHeight = m.FPDF_GetPageHeightF(pagePtr);
 
-  if (title) {
-    entries.Contents = PDFString.of(title);
-  }
+      const annotPtr = m.FPDFPage_CreateAnnot(pagePtr, FPDF_ANNOT_LINK);
+      if (!annotPtr) {
+        throw new Error('Failed to create link annotation');
+      }
 
-  const annotDict = ctx.obj(entries);
+      try {
+        // Set rect (convert from CSS top-left to PDF bottom-left origin)
+        // FS_RECTF layout: { left, top, right, bottom } where top > bottom in PDF coords
+        const pdfLeft = rect.x;
+        const pdfTop = pageHeight - rect.y;                 // CSS y=0 → PDF top
+        const pdfRight = rect.x + rect.width;
+        const pdfBottom = pageHeight - rect.y - rect.height;   // CSS bottom → PDF bottom
 
-  if (borderStyle !== 'solid' && borderWidth > 0) {
-    const bsDict = ctx.obj({
-      W: borderWidth,
-      S: PDFName.of(borderStyleCode(borderStyle)),
-    });
-    (annotDict as PDFDict).set(PDFName.of('BS'), bsDict);
-  }
+        const rectBuf = m.pdfium.wasmExports.malloc(4 * 4);
+        m.pdfium.setValue(rectBuf, pdfLeft, 'float');   // offset 0: left
+        m.pdfium.setValue(rectBuf + 4, pdfTop, 'float');   // offset 4: top  (larger y)
+        m.pdfium.setValue(rectBuf + 8, pdfRight, 'float');   // offset 8: right
+        m.pdfium.setValue(rectBuf + 12, pdfBottom, 'float');   // offset 12: bottom (smaller y)
+        m.FPDFAnnot_SetRect(annotPtr, rectBuf);
+        m.pdfium.wasmExports.free(rectBuf);
 
-  if (url) {
-    const actionDict = ctx.obj({
-      S: 'URI',
-      URI: PDFString.of(url),
-    });
-    (annotDict as PDFDict).set(PDFName.of('A'), actionDict);
-  } else if (destinationPage !== undefined) {
-    const destPage = pdfDoc.getPage(destinationPage);
-    const destArray = ctx.obj([destPage.ref, 'XYZ', null, null, null]);
-    (annotDict as PDFDict).set(PDFName.of('Dest'), destArray);
-  }
+        // Set color
+        // FPDFANNOT_COLORTYPE_Color = 0
+        m.FPDFAnnot_SetColor(
+          annotPtr,
+          0,
+          Math.round(color[0] * 255),
+          Math.round(color[1] * 255),
+          Math.round(color[2] * 255),
+          255,
+        );
 
-  const annotRef = ctx.register(annotDict);
+        // Set border
+        m.FPDFAnnot_SetBorder(annotPtr, 0, 0, borderWidth);
 
-  const existingAnnots = page.node.get(PDFName.of('Annots'));
-  if (existingAnnots) {
-    const resolvedAnnots =
-      existingAnnots instanceof PDFRef ? ctx.lookup(existingAnnots) : existingAnnots;
-    if (resolvedAnnots instanceof PDFArray) {
-      resolvedAnnots.push(annotRef);
-    } else {
-      page.node.set(PDFName.of('Annots'), ctx.obj([annotRef]));
+        // Set URI for external links
+        if (url) {
+          const uriPtr = writeUtf16(m, url);
+          m.FPDFAnnot_SetURI(annotPtr, uriPtr);
+          m.pdfium.wasmExports.free(uriPtr);
+        }
+
+        // Set title / contents
+        if (title) {
+          const titlePtr = writeUtf16(m, title);
+          m.FPDFAnnot_SetStringValue(annotPtr, 'Contents', titlePtr);
+          m.pdfium.wasmExports.free(titlePtr);
+        }
+      } finally {
+        m.FPDFPage_CloseAnnot(annotPtr);
+      }
+    } finally {
+      m.FPDF_ClosePage(pagePtr);
     }
-  } else {
-    page.node.set(PDFName.of('Annots'), ctx.obj([annotRef]));
+
+    return await saveRawDocument(docPtr);
+
+  } finally {
+    closeDocAndFreeBuffer(m, docPtr);
   }
 }
 
 /**
- * Remove a link annotation from a page by its index in the /Annots array.
- * Returns true if the annotation was found and removed.
+ * Remove a link annotation from a page by its index.
+ * Returns the updated PDF bytes.
  */
-export function removeLinkAnnotation(
-  pdfDoc: PDFDocument,
-  page: PDFPage,
+export async function removeLinkAnnotation(
+  data: ArrayBuffer | Uint8Array,
+  pageIndex: number,
   annotIndex: number,
-): boolean {
-  const ctx = pdfDoc.context;
-  const annotsRaw = page.node.get(PDFName.of('Annots'));
-  if (!annotsRaw) return false;
+  password?: string,
+): Promise<ArrayBuffer> {
+  const m = await getPdfiumModule();
+  const docPtr = await openRawDocumentSafe(data, password);
 
-  const annots =
-    annotsRaw instanceof PDFRef ? ctx.lookup(annotsRaw) : annotsRaw;
-  if (!(annots instanceof PDFArray)) return false;
+  try {
+    const pagePtr = m.FPDF_LoadPage(docPtr, pageIndex);
+    if (!pagePtr) throw new Error(`Failed to load page ${pageIndex}`);
 
-  if (annotIndex < 0 || annotIndex >= annots.size()) return false;
+    m.FPDFPage_RemoveAnnot(pagePtr, annotIndex);
+    m.FPDF_ClosePage(pagePtr);
 
-  const entry = annots.get(annotIndex);
-  if (entry instanceof PDFRef) {
-    ctx.delete(entry);
+    return await saveRawDocument(docPtr);
+  } finally {
+    closeDocAndFreeBuffer(m, docPtr);
   }
-
-  annots.remove(annotIndex);
-
-  if (annots.size() === 0) {
-    page.node.delete(PDFName.of('Annots'));
-  }
-
-  return true;
 }
 
 /**
  * Extract all link annotations from a given PDF page.
  */
-export function extractLinksFromPage(
-  doc: PDFDocument,
-  page: PDFPage,
+export async function extractLinksFromPage(
+  data: ArrayBuffer | Uint8Array,
   pageIndex: number,
-): PdfLibLink[] {
-  const links: PdfLibLink[] = [];
-  const ctx = doc.context;
-  const { height: pageHeight } = page.getSize();
+  password?: string,
+): Promise<{ links: PdfLibLink[]; pdfPageWidth: number; pdfPageHeight: number }> {
+  const m = await getPdfiumModule();
+  const docPtr = await openRawDocumentSafe(data, password);
 
-  const annotsRaw = page.node.get(PDFName.of('Annots'));
-  if (!annotsRaw) return links;
+  try {
+    const pagePtr = m.FPDF_LoadPage(docPtr, pageIndex);
+    if (!pagePtr) return { links: [], pdfPageWidth: 0, pdfPageHeight: 0 };
 
-  const annots = annotsRaw instanceof PDFRef ? ctx.lookup(annotsRaw) : annotsRaw;
-  if (!(annots instanceof PDFArray)) return links;
+    const pageWidth = m.FPDF_GetPageWidthF(pagePtr);
+    const pageHeight = m.FPDF_GetPageHeightF(pagePtr);
+    const links: PdfLibLink[] = [];
+    const annotCount = m.FPDFPage_GetAnnotCount(pagePtr);
 
-  for (let i = 0; i < annots.size(); i++) {
-    try {
-      const annotRaw = annots.get(i);
-      const annot = annotRaw instanceof PDFRef ? ctx.lookup(annotRaw) : annotRaw;
-      if (!(annot instanceof PDFDict)) continue;
+    for (let i = 0; i < annotCount; i++) {
+      try {
+        const annotPtr = m.FPDFPage_GetAnnot(pagePtr, i);
+        if (!annotPtr) continue;
 
-      const subtype = annot.get(PDFName.of('Subtype'));
-      if (subtype?.toString() !== '/Link') continue;
+        const subtype = m.FPDFAnnot_GetSubtype(annotPtr);
+        if (subtype !== FPDF_ANNOT_LINK) {
+          m.FPDFPage_CloseAnnot(annotPtr);
+          continue;
+        }
 
-      const rectRaw = annot.get(PDFName.of('Rect'));
-      const rect = rectRaw instanceof PDFRef ? ctx.lookup(rectRaw) : rectRaw;
-      if (!(rect instanceof PDFArray) || rect.size() < 4) continue;
+        // Get rect (CropBox-adjusted for correct overlay positioning)
+        const rectBuf = m.pdfium.wasmExports.malloc(4 * 4);
+        const hasRect = readAnnotRectAdjusted(m, annotPtr, rectBuf);
+        if (!hasRect) {
+          m.pdfium.wasmExports.free(rectBuf);
+          m.FPDFPage_CloseAnnot(annotPtr);
+          continue;
+        }
 
-      const x1 = num(ctx, rect.get(0));
-      const y1 = num(ctx, rect.get(1));
-      const x2 = num(ctx, rect.get(2));
-      const y2 = num(ctx, rect.get(3));
+        const rect = parseRectToCss(m, rectBuf, pageHeight);
+        m.pdfium.wasmExports.free(rectBuf);
 
-      const left = Math.min(x1, x2);
-      const bottom = Math.min(y1, y2);
-      const width = Math.abs(x2 - x1);
-      const height = Math.abs(y2 - y1);
+        // Try to get link object
+        const linkPtr = m.FPDFAnnot_GetLink(annotPtr);
+        let linkType: LinkType = 'unknown';
+        let targetPage: number | undefined;
+        let uri: string | undefined;
 
-      const top = pageHeight - bottom - height;
-
-      let linkType: LinkType = 'unknown';
-      let targetPage: number | undefined;
-      let uri: string | undefined;
-
-      const actionRaw = annot.get(PDFName.of('A'));
-      const action = actionRaw instanceof PDFRef ? ctx.lookup(actionRaw) : actionRaw;
-
-      if (action instanceof PDFDict) {
-        const actionType = action.get(PDFName.of('S'))?.toString();
-
-        if (actionType === '/URI') {
-          linkType = 'external';
-          uri = str(ctx, action.get(PDFName.of('URI')));
-        } else if (actionType === '/GoTo') {
-          linkType = 'internal';
-          const dest = action.get(PDFName.of('D'));
-          const destResolved = dest instanceof PDFRef ? ctx.lookup(dest) : dest;
-          if (destResolved instanceof PDFArray) {
-            targetPage = resolveDestArray(doc, ctx, destResolved);
-          } else {
-            const destName = str(ctx, destResolved);
-            if (destName) {
-              targetPage = resolveNamedDest(doc, ctx, destName);
+        if (linkPtr) {
+          // Check for action
+          const actionPtr = m.FPDFLink_GetAction(linkPtr);
+          if (actionPtr) {
+            const actionType = m.FPDFAction_GetType(actionPtr);
+            if (actionType === PDFACTION_URI) {
+              const uriLen = m.FPDFAction_GetURIPath(docPtr, actionPtr, 0, 0);
+              if (uriLen > 0) {
+                const uriBuf = m.pdfium.wasmExports.malloc(uriLen);
+                m.FPDFAction_GetURIPath(docPtr, actionPtr, uriBuf, uriLen);
+                uri = m.pdfium.UTF8ToString(uriBuf);
+                m.pdfium.wasmExports.free(uriBuf);
+                linkType = 'external';
+              }
+            } else if (actionType === PDFACTION_GOTO) {
+              const destPtr = m.FPDFAction_GetDest(docPtr, actionPtr);
+              if (destPtr) {
+                targetPage = m.FPDFDest_GetDestPageIndex(docPtr, destPtr);
+                linkType = 'internal';
+              }
             }
           }
-        } else if (actionType === '/GoToR' || actionType === '/Launch') {
-          linkType = 'external';
-          uri = str(ctx, action.get(PDFName.of('F')));
-        }
-      }
 
-      if (linkType === 'unknown') {
-        const destRaw = annot.get(PDFName.of('Dest'));
-        const dest = destRaw instanceof PDFRef ? ctx.lookup(destRaw) : destRaw;
-
-        if (dest instanceof PDFArray) {
-          linkType = 'internal';
-          targetPage = resolveDestArray(doc, ctx, dest);
-        } else {
-          const destName = str(ctx, dest);
-          if (destName) {
-            linkType = 'internal';
-            targetPage = resolveNamedDest(doc, ctx, destName);
+          // Check for direct destination
+          if (linkType === 'unknown') {
+            const destPtr = m.FPDFLink_GetDest(docPtr, linkPtr);
+            if (destPtr) {
+              targetPage = m.FPDFDest_GetDestPageIndex(docPtr, destPtr);
+              linkType = 'internal';
+            }
           }
         }
-      }
 
-      const title = extractTitle(ctx, annot);
-      const color = extractColor(ctx, annot);
-      const borderStyle = extractBorderStyle(ctx, annot);
-      const highlightMode = parseHighlightMode(ctx, annot.get(PDFName.of('H')));
-
-      links.push({
-        id: `pdflib-link-${pageIndex}-${i}`,
-        annotIndex: i,
-        rect: { x: left, y: top, width, height },
-        type: linkType,
-        targetPage,
-        uri,
-        title,
-        color,
-        borderStyle,
-        highlightMode,
-      });
-    } catch (e) {
-      console.warn('[pdfLinkUtils] Failed to parse annotation:', e);
-    }
-  }
-
-  return links;
-}
-
-// ---------------------------------------------------------------------------
-// Private Helpers (Internal to extraction logic)
-// ---------------------------------------------------------------------------
-
-function num(ctx: PDFContext, value: unknown): number {
-  const resolved = value instanceof PDFRef ? ctx.lookup(value) : value;
-  if (resolved instanceof PDFNumber) return resolved.asNumber();
-  if (typeof resolved === 'number') return resolved;
-  return 0;
-}
-
-function str(ctx: PDFContext, value: unknown): string | undefined {
-  const resolved = value instanceof PDFRef ? ctx.lookup(value) : value;
-  if (resolved instanceof PDFString) return resolved.decodeText();
-  if (resolved instanceof PDFHexString) return resolved.decodeText();
-  if (typeof resolved === 'string') return resolved;
-  return undefined;
-}
-
-function resolvePageIndex(doc: PDFDocument, pageRef: PDFRef): number | undefined {
-  const pages = doc.getPages();
-  for (let i = 0; i < pages.length; i++) {
-    const ref = pages[i].ref;
-    if (
-      ref === pageRef ||
-      (ref.objectNumber === pageRef.objectNumber &&
-        ref.generationNumber === pageRef.generationNumber)
-    ) {
-      return i;
-    }
-  }
-  return undefined;
-}
-
-function resolveDestArray(
-  doc: PDFDocument,
-  ctx: PDFContext,
-  destArr: PDFArray,
-): number | undefined {
-  if (destArr.size() < 1) return undefined;
-  const first = destArr.get(0);
-  if (first instanceof PDFRef) {
-    return resolvePageIndex(doc, first);
-  }
-  const n = num(ctx, first);
-  if (typeof n === 'number' && n >= 0) return n;
-  return undefined;
-}
-
-function resolveNamedDest(
-  doc: PDFDocument,
-  ctx: PDFContext,
-  name: string,
-): number | undefined {
-  try {
-    const catalog = doc.catalog;
-
-    const namesRaw = catalog.get(PDFName.of('Names'));
-    const namesDict = namesRaw instanceof PDFRef ? ctx.lookup(namesRaw) : namesRaw;
-    if (namesDict instanceof PDFDict) {
-      const destsRaw = namesDict.get(PDFName.of('Dests'));
-      const destsTree = destsRaw instanceof PDFRef ? ctx.lookup(destsRaw) : destsRaw;
-      if (destsTree instanceof PDFDict) {
-        const result = searchNameTree(doc, ctx, destsTree, name);
-        if (result !== undefined) return result;
-      }
-    }
-
-    const destsRaw = catalog.get(PDFName.of('Dests'));
-    const destsDict = destsRaw instanceof PDFRef ? ctx.lookup(destsRaw) : destsRaw;
-    if (destsDict instanceof PDFDict) {
-      const dest = destsDict.get(PDFName.of(name));
-      const destResolved = dest instanceof PDFRef ? ctx.lookup(dest) : dest;
-      if (destResolved instanceof PDFArray) {
-        return resolveDestArray(doc, ctx, destResolved);
-      }
-    }
-  } catch {
-    // ignore
-  }
-  return undefined;
-}
-
-function searchNameTree(
-  doc: PDFDocument,
-  ctx: PDFContext,
-  node: PDFDict,
-  name: string,
-): number | undefined {
-  const namesArr = node.get(PDFName.of('Names'));
-  const resolved = namesArr instanceof PDFRef ? ctx.lookup(namesArr) : namesArr;
-  if (resolved instanceof PDFArray) {
-    for (let i = 0; i < resolved.size(); i += 2) {
-      const key = str(ctx, resolved.get(i));
-      if (key === name) {
-        const val = resolved.get(i + 1);
-        const valResolved = val instanceof PDFRef ? ctx.lookup(val) : val;
-        if (valResolved instanceof PDFArray) {
-          return resolveDestArray(doc, ctx, valResolved);
+        // Get title from /Contents
+        let title: string | undefined;
+        const contentsLen = m.FPDFAnnot_GetStringValue(annotPtr, 'Contents', 0, 0);
+        if (contentsLen > 2) {
+          const contentsBuf = m.pdfium.wasmExports.malloc(contentsLen);
+          m.FPDFAnnot_GetStringValue(annotPtr, 'Contents', contentsBuf, contentsLen);
+          title = readUtf16(m, contentsBuf, contentsLen) || undefined;
+          m.pdfium.wasmExports.free(contentsBuf);
         }
-        if (valResolved instanceof PDFDict) {
-          const d = valResolved.get(PDFName.of('D'));
-          const dResolved = d instanceof PDFRef ? ctx.lookup(d) : d;
-          if (dResolved instanceof PDFArray) {
-            return resolveDestArray(doc, ctx, dResolved);
-          }
+
+        // Get color
+        let color: [number, number, number] | undefined;
+        // allocate 4 uint for RGBA
+        const rPtr = m.pdfium.wasmExports.malloc(16);
+        const gPtr = rPtr + 4;
+        const bPtr = rPtr + 8;
+        const aPtr = rPtr + 12;
+        const hasColor = m.FPDFAnnot_GetColor(annotPtr, 0, rPtr, gPtr, bPtr, aPtr);
+        if (hasColor) {
+          color = [
+            m.pdfium.getValue(rPtr, 'i32') / 255,
+            m.pdfium.getValue(gPtr, 'i32') / 255,
+            m.pdfium.getValue(bPtr, 'i32') / 255,
+          ];
         }
+        m.pdfium.wasmExports.free(rPtr);
+
+        links.push({
+          id: `link-${pageIndex}-${i}`,
+          annotIndex: i,
+          rect,
+          type: linkType,
+          targetPage,
+          uri,
+          title,
+          color,
+        });
+
+        m.FPDFPage_CloseAnnot(annotPtr);
+      } catch (e) {
+        console.warn('[pdfLinkUtils] Failed to parse annotation:', e);
       }
     }
-  }
 
-  const kidsArr = node.get(PDFName.of('Kids'));
-  const kidsResolved = kidsArr instanceof PDFRef ? ctx.lookup(kidsArr) : kidsArr;
-  if (kidsResolved instanceof PDFArray) {
-    for (let i = 0; i < kidsResolved.size(); i++) {
-      const kidRef = kidsResolved.get(i);
-      const kid = kidRef instanceof PDFRef ? ctx.lookup(kidRef) : kidRef;
-      if (kid instanceof PDFDict) {
-        const limits = kid.get(PDFName.of('Limits'));
-        const limitsResolved = limits instanceof PDFRef ? ctx.lookup(limits) : limits;
-        if (limitsResolved instanceof PDFArray && limitsResolved.size() >= 2) {
-          const lo = str(ctx, limitsResolved.get(0)) ?? '';
-          const hi = str(ctx, limitsResolved.get(1)) ?? '';
-          if (name < lo || name > hi) continue;
-        }
-        const result = searchNameTree(doc, ctx, kid, name);
-        if (result !== undefined) return result;
-      }
-    }
-  }
-
-  return undefined;
-}
-
-function borderStyleCode(style: LinkBorderStyle): string {
-  switch (style) {
-    case 'dashed':    return 'D';
-    case 'beveled':   return 'B';
-    case 'inset':     return 'I';
-    case 'underline': return 'U';
-    default:          return 'S';
+    m.FPDF_ClosePage(pagePtr);
+    return { links, pdfPageWidth: pageWidth, pdfPageHeight: pageHeight };
+  } finally {
+    closeDocAndFreeBuffer(m, docPtr);
   }
 }
-
-function highlightModeCode(mode: LinkHighlightMode): string {
-  switch (mode) {
-    case 'none':    return 'N';
-    case 'outline': return 'O';
-    case 'push':    return 'P';
-    default:        return 'I';
-  }
-}
-
-function parseBorderStyleName(ctx: PDFContext, value: unknown): LinkBorderStyle {
-  if (!value) return 'solid';
-  const resolved = value instanceof PDFRef ? ctx.lookup(value) : value;
-  const s = resolved instanceof PDFName ? resolved.decodeText() : String(resolved);
-  switch (s) {
-    case 'D': return 'dashed';
-    case 'B': return 'beveled';
-    case 'I': return 'inset';
-    case 'U': return 'underline';
-    default:  return 'solid';
-  }
-}
-
-function parseHighlightMode(ctx: PDFContext, value: unknown): LinkHighlightMode {
-  if (!value) return 'invert';
-  const resolved = value instanceof PDFRef ? ctx.lookup(value) : value;
-  const s = resolved instanceof PDFName ? resolved.decodeText() : String(resolved);
-  switch (s) {
-    case 'N': return 'none';
-    case 'I': return 'invert';
-    case 'O': return 'outline';
-    case 'P': return 'push';
-    default:  return 'invert';
-  }
-}
-
-function extractBorderStyle(
-  ctx: PDFContext,
-  annot: PDFDict,
-): PdfLibLink['borderStyle'] | undefined {
-  const bsRaw = annot.get(PDFName.of('BS'));
-  const bs = bsRaw instanceof PDFRef ? ctx.lookup(bsRaw) : bsRaw;
-  if (bs instanceof PDFDict) {
-    const w = bs.get(PDFName.of('W'));
-    const s = bs.get(PDFName.of('S'));
-    return {
-      width: num(ctx, w) || 1,
-      style: parseBorderStyleName(ctx, s),
-    };
-  }
-
-  const borderRaw = annot.get(PDFName.of('Border'));
-  const border = borderRaw instanceof PDFRef ? ctx.lookup(borderRaw) : borderRaw;
-  if (border instanceof PDFArray && border.size() >= 3) {
-    const width = num(ctx, border.get(2));
-    const style: LinkBorderStyle = border.size() >= 4 ? 'dashed' : 'solid';
-    return { width, style };
-  }
-
-  return undefined;
-}
-
-function extractColor(
-  ctx: PDFContext,
-  annot: PDFDict,
-): [number, number, number] | undefined {
-  const cRaw = annot.get(PDFName.of('C'));
-  const c = cRaw instanceof PDFRef ? ctx.lookup(cRaw) : cRaw;
-  if (!(c instanceof PDFArray)) return undefined;
-
-  const len = c.size();
-  if (len === 3) {
-    return [num(ctx, c.get(0)), num(ctx, c.get(1)), num(ctx, c.get(2))];
-  }
-  if (len === 1) {
-    const g = num(ctx, c.get(0));
-    return [g, g, g];
-  }
-  if (len === 4) {
-    const cVal = num(ctx, c.get(0));
-    const m = num(ctx, c.get(1));
-    const y = num(ctx, c.get(2));
-    const k = num(ctx, c.get(3));
-    return [
-      (1 - cVal) * (1 - k),
-      (1 - m) * (1 - k),
-      (1 - y) * (1 - k),
-    ];
-  }
-  return undefined;
-}
-
-function extractTitle(
-  ctx: PDFContext,
-  annot: PDFDict,
-): string | undefined {
-  const raw = annot.get(PDFName.of('Contents'));
-  const resolved = raw instanceof PDFRef ? ctx.lookup(raw) : raw;
-  if (resolved instanceof PDFString || resolved instanceof PDFHexString) {
-    return resolved.decodeText();
-  }
-  return undefined;
-}

frontend/src/core/utils/pdfiumBitmapUtils.ts

@@ -0,0 +1,208 @@
+/**
+ * pdfiumBitmapUtils — Shared utilities for working with PDFium WASM bitmaps.
+ *
+ * Centralises the RGBA→BGRA pixel conversion and image-to-page-object
+ * embedding that previously appeared (copy-pasted) in at least 5 files.
+ *
+ * Performance note: instead of calling `m.pdfium.setValue()` per pixel
+ * (which crosses the JS↔WASM FFI boundary on every call), we perform
+ * the colour-channel swizzle in a plain JS TypedArray and then bulk-
+ * copy the result into the WASM heap with a single `HEAPU8.set()`.
+ */
+import type { WrappedPdfiumModule } from '@embedpdf/pdfium';
+
+/** FPDF_ANNOT_LINK */
+export const FPDF_ANNOT_LINK = 4;
+/** FPDF_ANNOT_WIDGET (form field) */
+export const FPDF_ANNOT_WIDGET = 20;
+/** FPDF_ANNOT_INK */
+export const FPDF_ANNOT_INK = 15;
+/** FPDF_ANNOT_LINE */
+export const FPDF_ANNOT_LINE = 3;
+/** PDFACTION_GOTO */
+export const PDFACTION_GOTO = 1;
+/** PDFACTION_URI */
+export const PDFACTION_URI = 3;
+/** FLAT_PRINT (for FPDFPage_Flatten) */
+export const FLAT_PRINT = 2;
+
+/**
+ * Convert an RGBA pixel buffer to BGRA (PDFium's expected format) **in place
+ * inside the WASM heap** with a single bulk memcpy.
+ *
+ * When `stride === width * 4` the copy is a single `HEAPU8.set()`.
+ * When the bitmap has padding (stride > width * 4), rows are copied
+ * individually to skip the padding bytes.
+ *
+ * This is ~100× faster than per-pixel `m.pdfium.setValue()` calls for
+ * large images.
+ */
+export function copyRgbaToBgraHeap(
+  m: WrappedPdfiumModule,
+  rgba: Uint8Array | Uint8ClampedArray,
+  bufferPtr: number,
+  width: number,
+  height: number,
+  stride: number,
+): void {
+  const rowBytes = width * 4;
+
+  if (stride === rowBytes) {
+    // Fast path: no padding — single bulk copy after swizzle
+    const bgra = new Uint8Array(rgba.length);
+    for (let i = 0; i < rgba.length; i += 4) {
+      bgra[i]     = rgba[i + 2]; // B
+      bgra[i + 1] = rgba[i + 1]; // G
+      bgra[i + 2] = rgba[i];     // R
+      bgra[i + 3] = rgba[i + 3]; // A
+    }
+    new Uint8Array(
+      (m.pdfium.wasmExports as any).memory.buffer,
+    ).set(bgra, bufferPtr);
+  } else {
+    // Stride has padding — swizzle + copy row by row
+    const rowBuf = new Uint8Array(rowBytes);
+    const heap = new Uint8Array(
+      (m.pdfium.wasmExports as any).memory.buffer,
+    );
+    for (let y = 0; y < height; y++) {
+      const srcRowStart = y * rowBytes;
+      for (let x = 0; x < rowBytes; x += 4) {
+        rowBuf[x]     = rgba[srcRowStart + x + 2]; // B
+        rowBuf[x + 1] = rgba[srcRowStart + x + 1]; // G
+        rowBuf[x + 2] = rgba[srcRowStart + x];     // R
+        rowBuf[x + 3] = rgba[srcRowStart + x + 3]; // A
+      }
+      heap.set(rowBuf, bufferPtr + y * stride);
+    }
+  }
+}
+export interface DecodedImage {
+  rgba: Uint8Array;
+  width: number;
+  height: number;
+}
+
+/**
+ * Create a PDFium bitmap from decoded RGBA pixels, attach it to a new image
+ * page object, position it via an affine matrix, and insert it into the page.
+ *
+ * Returns `true` if the image was successfully inserted, `false` otherwise.
+ * All intermediate WASM resources are cleaned up on failure.
+ */
+export function embedBitmapImageOnPage(
+  m: WrappedPdfiumModule,
+  docPtr: number,
+  pagePtr: number,
+  image: DecodedImage,
+  pdfX: number,
+  pdfY: number,
+  drawWidth: number,
+  drawHeight: number,
+): boolean {
+  const bitmapPtr = m.FPDFBitmap_Create(image.width, image.height, 1);
+  if (!bitmapPtr) return false;
+
+  try {
+    const bufferPtr = m.FPDFBitmap_GetBuffer(bitmapPtr);
+    const stride = m.FPDFBitmap_GetStride(bitmapPtr);
+
+    copyRgbaToBgraHeap(m, image.rgba, bufferPtr, image.width, image.height, stride);
+
+    const imageObjPtr = m.FPDFPageObj_NewImageObj(docPtr);
+    if (!imageObjPtr) return false;
+
+    const setBitmapOk = m.FPDFImageObj_SetBitmap(pagePtr, 0, imageObjPtr, bitmapPtr);
+    if (!setBitmapOk) {
+      m.FPDFPageObj_Destroy(imageObjPtr);
+      return false;
+    }
+
+    // -- early-destroy the bitmap; PDFium has copied the pixel data internally
+    m.FPDFBitmap_Destroy(bitmapPtr);
+
+    // Set affine transform: [a b c d e f]
+    const matrixPtr = m.pdfium.wasmExports.malloc(6 * 4);
+    try {
+      m.pdfium.setValue(matrixPtr,      drawWidth,  'float'); // a — scaleX
+      m.pdfium.setValue(matrixPtr + 4,  0,          'float'); // b
+      m.pdfium.setValue(matrixPtr + 8,  0,          'float'); // c
+      m.pdfium.setValue(matrixPtr + 12, drawHeight, 'float'); // d — scaleY
+      m.pdfium.setValue(matrixPtr + 16, pdfX,       'float'); // e — translateX
+      m.pdfium.setValue(matrixPtr + 20, pdfY,       'float'); // f — translateY
+
+      if (!m.FPDFPageObj_SetMatrix(imageObjPtr, matrixPtr)) {
+        m.FPDFPageObj_Destroy(imageObjPtr);
+        return false;
+      }
+    } finally {
+      m.pdfium.wasmExports.free(matrixPtr);
+    }
+
+    m.FPDFPage_InsertObject(pagePtr, imageObjPtr);
+    return true;
+  } finally {
+    // Safety net: FPDFBitmap_Destroy is a no-op if ptr is 0 in most PDFium
+    // builds but guard anyway.  If already destroyed above, the second call
+    // is harmless because we allow it to be idempotent.
+    // We use a try-catch to be safe across PDFium WASM builds.
+    try { m.FPDFBitmap_Destroy(bitmapPtr); } catch { /* already freed */ }
+  }
+}
+/**
+ * Draw a simple light-grey rectangle as a placeholder for annotations
+ * that could not be rendered.
+ */
+export function drawPlaceholderRect(
+  m: WrappedPdfiumModule,
+  pagePtr: number,
+  x: number,
+  y: number,
+  width: number,
+  height: number,
+): void {
+  const pathPtr = m.FPDFPageObj_CreateNewPath(x, y);
+  if (!pathPtr) return;
+
+  m.FPDFPath_LineTo(pathPtr, x + width, y);
+  m.FPDFPath_LineTo(pathPtr, x + width, y + height);
+  m.FPDFPath_LineTo(pathPtr, x, y + height);
+  m.FPDFPath_Close(pathPtr);
+
+  m.FPDFPageObj_SetFillColor(pathPtr, 230, 230, 230, 150);
+  m.FPDFPageObj_SetStrokeColor(pathPtr, 128, 128, 128, 255);
+  m.FPDFPageObj_SetStrokeWidth(pathPtr, 1);
+
+  // fillMode 1 = alternate fill, stroke = true
+  m.FPDFPath_SetDrawMode(pathPtr, 1, true);
+
+  m.FPDFPage_InsertObject(pagePtr, pathPtr);
+}
+
+/**
+ * Decode an image data URL (e.g. `data:image/png;base64,...`) to raw RGBA
+ * pixel data via an offscreen canvas.
+ */
+export function decodeImageDataUrl(dataUrl: string): Promise<DecodedImage | null> {
+  return new Promise((resolve) => {
+    const img = new Image();
+    img.onload = () => {
+      try {
+        const canvas = document.createElement('canvas');
+        canvas.width = img.width;
+        canvas.height = img.height;
+        const ctx = canvas.getContext('2d');
+        if (!ctx) { resolve(null); return; }
+        ctx.drawImage(img, 0, 0);
+        const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
+        resolve({
+          rgba: new Uint8Array(imageData.data.buffer),
+          width: canvas.width,
+          height: canvas.height,
+        });
+      } catch { resolve(null); }
+    };
+    img.onerror = () => resolve(null);
+    img.src = dataUrl;
+  });
+}

frontend/src/core/utils/signatureFlattening.ts

@@ -1,9 +1,21 @@
-import {PDFDocument, rgb} from '@cantoo/pdf-lib';
-import {PdfAnnotationSubtype} from '@embedpdf/models';
-import {generateThumbnailWithMetadata} from '@app/utils/thumbnailUtils';
-import {createChildStub, createProcessedFile} from '@app/contexts/file/fileActions';
-import {createStirlingFile, FileId, StirlingFile, StirlingFileStub} from '@app/types/fileContext';
-import type {SignatureAPI} from '@app/components/viewer/viewerTypes';
+// PDFium annotation subtype constants
+import {
+  FPDF_ANNOT_INK,
+  FPDF_ANNOT_LINE,
+  embedBitmapImageOnPage,
+  drawPlaceholderRect,
+  decodeImageDataUrl,
+} from '@app/utils/pdfiumBitmapUtils';
+import { generateThumbnailWithMetadata } from '@app/utils/thumbnailUtils';
+import { createChildStub, createProcessedFile } from '@app/contexts/file/fileActions';
+import { createStirlingFile, FileId, StirlingFile, StirlingFileStub } from '@app/types/fileContext';
+import type { SignatureAPI } from '@app/components/viewer/viewerTypes';
+import {
+  getPdfiumModule,
+  openRawDocumentSafe,
+  closeDocAndFreeBuffer,
+  saveRawDocument,
+} from '@app/services/pdfiumService';
 
 interface MinimalFileContextSelectors {
   getAllFileIds: () => FileId[];
@@ -37,7 +49,6 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
     const allAnnotations: Array<{pageIndex: number, annotations: any[]}> = [];
 
     if (signatureApiRef?.current) {
-
       const scrollState = getScrollState();
       const totalPages = scrollState.totalPages;
 
@@ -47,7 +58,6 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
           if (pageAnnotations && pageAnnotations.length > 0) {
             const sessionAnnotations = pageAnnotations.filter(annotation => {
               const hasStoredImageData = annotation.id && getImageData(annotation.id);
-
               const hasDirectImageData = annotation.imageData || annotation.appearance ||
                                        annotation.stampData || annotation.imageSrc ||
                                        annotation.contents || annotation.data;
@@ -64,7 +74,7 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
       }
     }
 
-    // Step 2: Delete ONLY session annotations from EmbedPDF before export (they'll be rendered manually)
+    // Step 2: Delete ONLY session annotations from EmbedPDF before export
     if (allAnnotations.length > 0 && signatureApiRef?.current) {
       for (const pageData of allAnnotations) {
         for (const annotation of pageData.annotations) {
@@ -77,7 +87,7 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
       }
     }
 
-    // Step 3: Use EmbedPDF's saveAsCopy to get the original PDF (now without annotations)
+    // Step 3: Use EmbedPDF's saveAsCopy to get the original PDF
     if (!exportActions) {
       console.error('No export actions available');
       return null;
@@ -85,7 +95,6 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
     const pdfArrayBuffer = await exportActions.saveAsCopy();
 
     if (pdfArrayBuffer) {
-
       const blob = new Blob([pdfArrayBuffer], { type: 'application/pdf' });
 
       let currentFile = originalFile;
@@ -108,182 +117,85 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
 
       let signedFile = new File([blob], currentFile.name, { type: 'application/pdf' });
 
-      // Step 4: Manually render extracted annotations onto the PDF using PDF-lib
+      // Step 4: Manually render extracted annotations onto the PDF using PDFium WASM
       if (allAnnotations.length > 0) {
         try {
           const pdfArrayBufferForFlattening = await signedFile.arrayBuffer();
+          const m = await getPdfiumModule();
+          const docPtr = await openRawDocumentSafe(pdfArrayBufferForFlattening);
 
-          let pdfDoc: PDFDocument;
           try {
-            pdfDoc = await PDFDocument.load(pdfArrayBufferForFlattening, {
-              ignoreEncryption: true,
-              capNumbers: false,
-              throwOnInvalidObject: false
-            });
-          } catch {
-            console.warn('Failed to load with standard options, trying createProxy...');
-            try {
-              pdfDoc = await PDFDocument.create();
-              const sourcePdf = await PDFDocument.load(pdfArrayBufferForFlattening, {
-                ignoreEncryption: true,
-                throwOnInvalidObject: false
-              });
-              const pageIndices = sourcePdf.getPages().map((_, i) => i);
-              const copiedPages = await pdfDoc.copyPages(sourcePdf, pageIndices);
-              copiedPages.forEach(page => pdfDoc.addPage(page));
-            } catch (copyError) {
-              console.error('Failed to load PDF with any method:', copyError);
-              throw copyError;
-            }
-          }
+            const pageCount = m.FPDF_GetPageCount(docPtr);
 
-          const pages = pdfDoc.getPages();
+            for (const pageData of allAnnotations) {
+              const { pageIndex, annotations } = pageData;
 
-          for (const pageData of allAnnotations) {
-            const { pageIndex, annotations } = pageData;
+              if (pageIndex < pageCount) {
+                const pagePtr = m.FPDF_LoadPage(docPtr, pageIndex);
+                if (!pagePtr) continue;
 
-            if (pageIndex < pages.length) {
-              const page = pages[pageIndex];
-              const { height: pageHeight } = page.getSize();
+                const pageHeight = m.FPDF_GetPageHeightF(pagePtr);
 
-              for (const annotation of annotations) {
-                try {
+                for (const annotation of annotations) {
+                  try {
+                    const rect = annotation.rect || annotation.bounds || annotation.rectangle || annotation.position;
 
-                  const rect = annotation.rect || annotation.bounds || annotation.rectangle || annotation.position;
+                    if (rect) {
+                      const originalX = rect.origin?.x || rect.x || rect.left || 0;
+                      const originalY = rect.origin?.y || rect.y || rect.top || 0;
+                      const width = rect.size?.width || rect.width || 100;
+                      const height = rect.size?.height || rect.height || 50;
 
-                  if (rect) {
-                    const originalX = rect.origin?.x || rect.x || rect.left || 0;
-                    const originalY = rect.origin?.y || rect.y || rect.top || 0;
-                    const width = rect.size?.width || rect.width || 100;
-                    const height = rect.size?.height || rect.height || 50;
+                      // Convert from CSS top-left to PDF bottom-left
+                      const pdfX = originalX;
+                      const pdfY = pageHeight - originalY - height;
 
-                    const pdfX = originalX;
-                    const pdfY = pageHeight - originalY - height;
+                      let imageDataUrl = annotation.imageData || annotation.appearance || annotation.stampData ||
+                                       annotation.imageSrc || annotation.contents || annotation.data;
 
-
-                    let imageDataUrl = annotation.imageData || annotation.appearance || annotation.stampData ||
-                                     annotation.imageSrc || annotation.contents || annotation.data;
-
-                    if (!imageDataUrl && annotation.id) {
-                      const storedImageData = getImageData(annotation.id);
-                      if (storedImageData) {
-                        imageDataUrl = storedImageData;
-                      }
-                    }
-
-                    if (imageDataUrl && typeof imageDataUrl === 'string' && imageDataUrl.startsWith('data:image/svg+xml')) {
-                      let svgRendered = false;
-                      try {
-                        const svgContent = decodeSvgDataUrl(imageDataUrl);
-                        if (svgContent && typeof (page as any).drawSvg === 'function') {
-                          // drawSvg from @cantoo/pdf-lib renders SVG natively as
-                          (page as any).drawSvg(svgContent, {
-                            x: pdfX,
-                            y: pdfY,
-                            width: width,
-                            height: height,
-                          });
-                          svgRendered = true;
-                        }
-                      } catch (svgError) {
-                        console.warn('Native SVG embed failed, falling back to raster:', svgError);
-                      }
-
-                      if (!svgRendered) {
-                        try {
-                          const pngBytes = await rasteriseSvgToPng(imageDataUrl, width * 2, height * 2);
-                          if (pngBytes) {
-                            const image = await pdfDoc.embedPng(pngBytes);
-                            page.drawImage(image, { x: pdfX, y: pdfY, width, height });
-                            svgRendered = true;
-                          }
-                        } catch (rasterError) {
-                          console.error('SVG raster fallback also failed:', rasterError);
+                      if (!imageDataUrl && annotation.id) {
+                        const storedImageData = getImageData(annotation.id);
+                        if (storedImageData) {
+                          imageDataUrl = storedImageData;
                         }
                       }
 
-                      if (!svgRendered) {
-                        page.drawRectangle({
-                          x: pdfX,
-                          y: pdfY,
-                          width: width,
-                          height: height,
-                          borderColor: rgb(0.8, 0, 0),
-                          borderWidth: 1,
-                          color: rgb(1, 0.95, 0.95),
-                          opacity: 0.7,
-                        });
-                      }
-                    } else if (imageDataUrl && typeof imageDataUrl === 'string' && imageDataUrl.startsWith('data:image')) {
-                      try {
-                        const base64Data = imageDataUrl.split(',')[1];
-                        const imageBytes = Uint8Array.from(atob(base64Data), c => c.charCodeAt(0));
-
-                        let image;
-                        if (imageDataUrl.includes('data:image/jpeg') || imageDataUrl.includes('data:image/jpg')) {
-                          image = await pdfDoc.embedJpg(imageBytes);
-                        } else if (imageDataUrl.includes('data:image/png')) {
-                          image = await pdfDoc.embedPng(imageBytes);
+                      // Convert SVG to PNG first if needed
+                      if (imageDataUrl && typeof imageDataUrl === 'string' && imageDataUrl.startsWith('data:image/svg+xml')) {
+                        const pngBytes = await rasteriseSvgToPng(imageDataUrl, width * 2, height * 2);
+                        if (pngBytes) {
+                          imageDataUrl = await uint8ArrayToPngDataUrl(pngBytes);
                         } else {
-                          image = await pdfDoc.embedPng(imageBytes);
+                          drawPlaceholderRect(m, pagePtr, pdfX, pdfY, width, height);
+                          continue;
                         }
-
-                        page.drawImage(image, {
-                          x: pdfX,
-                          y: pdfY,
-                          width: width,
-                          height: height,
-                        });
-
-                      } catch (imageError) {
-                        console.error('Failed to render image annotation:', imageError);
                       }
-                    } else if (annotation.content || annotation.text) {
-                      page.drawText(annotation.content || annotation.text, {
-                        x: pdfX,
-                        y: pdfY + height - 12, // Adjust for text baseline
-                        size: 12,
-                        color: rgb(0, 0, 0)
-                      });
-                    } else if (annotation.type === PdfAnnotationSubtype.INK || annotation.type === PdfAnnotationSubtype.LINE) {
-                      page.drawRectangle({
-                        x: pdfX,
-                        y: pdfY,
-                        width: width,
-                        height: height,
-                        borderColor: rgb(0, 0, 0),
-                        borderWidth: 1,
-                        color: rgb(0.95, 0.95, 0.95),
-                        opacity: 0.6
-                      });
-                    } else {
-                      page.drawRectangle({
-                        x: pdfX,
-                        y: pdfY,
-                        width: width,
-                        height: height,
-                        borderColor: rgb(1, 0, 0),
-                        borderWidth: 2,
-                        color: rgb(1, 1, 0),
-                        opacity: 0.5
-                      });
+
+                      if (imageDataUrl && typeof imageDataUrl === 'string' && imageDataUrl.startsWith('data:image')) {
+                        // Decode the image data URL to raw pixels via canvas
+                        const imageResult = await decodeImageDataUrl(imageDataUrl);
+                        if (imageResult) {
+                          embedBitmapImageOnPage(m, docPtr, pagePtr, imageResult, pdfX, pdfY, width, height);
+                        }
+                      } else if (annotation.type === FPDF_ANNOT_INK || annotation.type === FPDF_ANNOT_LINE) {
+                        drawPlaceholderRect(m, pagePtr, pdfX, pdfY, width, height);
+                      }
                     }
+                  } catch (annotationError) {
+                    console.warn('Failed to render annotation:', annotationError);
                   }
-                } catch (annotationError) {
-                  console.warn('Failed to render annotation:', annotationError);
                 }
+
+                m.FPDFPage_GenerateContent(pagePtr);
+                m.FPDF_ClosePage(pagePtr);
               }
             }
+
+            const resultBuf = await saveRawDocument(docPtr);
+            signedFile = new File([resultBuf], currentFile.name, { type: 'application/pdf' });
+          } finally {
+            closeDocAndFreeBuffer(m, docPtr);
           }
-
-
-          const flattenedPdfBytes = await pdfDoc.save({ useObjectStreams: false, addDefaultPage: false });
-
-          const arrayBuffer = new ArrayBuffer(flattenedPdfBytes.length);
-          const uint8View = new Uint8Array(arrayBuffer);
-          uint8View.set(flattenedPdfBytes);
-          signedFile = new File([arrayBuffer], currentFile.name, { type: 'application/pdf' });
-
         } catch (renderError) {
           console.error('Failed to manually render annotations:', renderError);
           console.warn('Signatures may only show as annotations');
@@ -325,26 +237,19 @@ export async function flattenSignatures(options: SignatureFlatteningOptions): Pr
 }
 
 /**
- * Decode an SVG data URL to its raw XML string.
- * Handles both base64-encoded and URI-encoded SVG data URLs.
+ * Convert Uint8Array PNG bytes to a data URL for canvas decoding.
  */
-function decodeSvgDataUrl(dataUrl: string): string | null {
-  try {
-    if (dataUrl.includes(';base64,')) {
-      const base64 = dataUrl.split(',')[1];
-      return atob(base64);
-    }
-    // URI-encoded SVG
-    const encoded = dataUrl.split(',')[1];
-    return decodeURIComponent(encoded);
-  } catch {
-    return null;
-  }
+function uint8ArrayToPngDataUrl(pngBytes: Uint8Array): Promise<string> {
+  return new Promise((resolve) => {
+    const blob = new Blob([pngBytes as BlobPart], { type: 'image/png' });
+    const reader = new FileReader();
+    reader.onloadend = () => resolve(reader.result as string);
+    reader.readAsDataURL(blob);
+  });
 }
 
 /**
  * Rasterise an SVG data URL to PNG bytes via an offscreen canvas.
- * Used as a fallback when native SVG embedding is unavailable.
  */
 function rasteriseSvgToPng(svgDataUrl: string, width: number, height: number): Promise<Uint8Array | null> {
   return new Promise((resolve) => {
@@ -355,17 +260,11 @@ function rasteriseSvgToPng(svgDataUrl: string, width: number, height: number): P
         canvas.width = Math.max(1, Math.round(width));
         canvas.height = Math.max(1, Math.round(height));
         const ctx = canvas.getContext('2d');
-        if (!ctx) {
-          resolve(null);
-          return;
-        }
+        if (!ctx) { resolve(null); return; }
         ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
         canvas.toBlob(
           (blob) => {
-            if (!blob) {
-              resolve(null);
-              return;
-            }
+            if (!blob) { resolve(null); return; }
             blob.arrayBuffer().then(
               (buf) => resolve(new Uint8Array(buf)),
               () => resolve(null),
@@ -373,9 +272,7 @@ function rasteriseSvgToPng(svgDataUrl: string, width: number, height: number): P
           },
           'image/png',
         );
-      } catch {
-        resolve(null);
-      }
+      } catch { resolve(null); }
     };
     img.onerror = () => resolve(null);
     img.src = svgDataUrl;