Offline pdfium (#5213)

# Description of Changes

<!--
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)

### 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.

frontend/package-lock.json

@@ -105,6 +105,7 @@
         "typescript": "^5.9.2",
         "typescript-eslint": "^8.44.1",
         "vite": "^7.1.7",
+        "vite-plugin-static-copy": "^3.1.4",
         "vite-tsconfig-paths": "^5.1.4",
         "vitest": "^3.2.4"
       }
@@ -11093,6 +11094,19 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/p-map": {
+      "version": "7.0.4",
+      "resolved": "https://registry.npmjs.org/p-map/-/p-map-7.0.4.tgz",
+      "integrity": "sha512-tkAQEw8ysMzmkhgw8k+1U/iPhWNhykKnSk4Rd5zLoPJCuJaGRPo6YposrZgaxHKzDHdDWWZvE/Sk7hsL2X/CpQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
     "node_modules/pac-proxy-agent": {
       "version": "7.2.0",
       "resolved": "https://registry.npmjs.org/pac-proxy-agent/-/pac-proxy-agent-7.2.0.tgz",
@@ -14503,6 +14517,25 @@
         "url": "https://opencollective.com/vitest"
       }
     },
+    "node_modules/vite-plugin-static-copy": {
+      "version": "3.1.4",
+      "resolved": "https://registry.npmjs.org/vite-plugin-static-copy/-/vite-plugin-static-copy-3.1.4.tgz",
+      "integrity": "sha512-iCmr4GSw4eSnaB+G8zc2f4dxSuDjbkjwpuBLLGvQYR9IW7rnDzftnUjOH5p4RYR+d4GsiBqXRvzuFhs5bnzVyw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "chokidar": "^3.6.0",
+        "p-map": "^7.0.3",
+        "picocolors": "^1.1.1",
+        "tinyglobby": "^0.2.15"
+      },
+      "engines": {
+        "node": "^18.0.0 || >=20.0.0"
+      },
+      "peerDependencies": {
+        "vite": "^5.0.0 || ^6.0.0 || ^7.0.0"
+      }
+    },
     "node_modules/vite-tsconfig-paths": {
       "version": "5.1.4",
       "resolved": "https://registry.npmjs.org/vite-tsconfig-paths/-/vite-tsconfig-paths-5.1.4.tgz",

frontend/package.json

@@ -152,6 +152,7 @@
     "typescript": "^5.9.2",
     "typescript-eslint": "^8.44.1",
     "vite": "^7.1.7",
+    "vite-plugin-static-copy": "^3.1.4",
     "vite-tsconfig-paths": "^5.1.4",
     "vitest": "^3.2.4"
   },

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

@@ -46,6 +46,7 @@ import { PrintAPIBridge } from '@app/components/viewer/PrintAPIBridge';
 import { isPdfFile } from '@app/utils/fileUtils';
 import { useTranslation } from 'react-i18next';
 import { LinkLayer } from '@app/components/viewer/LinkLayer';
+import { absoluteWithBasePath } from '@app/constants/app';
 
 interface LocalEmbedPDFProps {
   file?: File | Blob;
@@ -167,8 +168,10 @@ export function LocalEmbedPDF({ file, url, enableAnnotations = false, onSignatur
     ];
   }, [pdfUrl]);
 
-  // Initialize the engine with the React hook
-  const { engine, isLoading, error } = usePdfiumEngine();
+  // Initialize the engine with the React hook - use local WASM for offline support
+  const { engine, isLoading, error } = usePdfiumEngine({
+    wasmUrl: absoluteWithBasePath('/pdfium/pdfium.wasm'),
+  });
 
 
   // Early return if no file or URL provided

frontend/vite.config.ts

@@ -1,6 +1,7 @@
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react-swc';
 import tsconfigPaths from 'vite-tsconfig-paths';
+import { viteStaticCopy } from 'vite-plugin-static-copy';
 
 export default defineConfig(({ mode }) => {
   // When DISABLE_ADDITIONAL_FEATURES is false (or unset), enable proprietary features
@@ -20,6 +21,15 @@ export default defineConfig(({ mode }) => {
       tsconfigPaths({
         projects: [tsconfigProject],
       }),
+      viteStaticCopy({
+        targets: [
+          {
+            //provides static pdfium so embedpdf can run without cdn
+            src: 'node_modules/@embedpdf/pdfium/dist/pdfium.wasm',
+            dest: 'pdfium'
+          }
+        ]
+      })
     ],
     server: {
       host: true,