update to add optional Zero Padding to page numbers (Bates Stamping).… (#5612)

… Useful in legal and other professional fields to have page numbers
written with padded 0s of a fixed width. This is also known as bates
stamping.

# Description of Changes

<!--
Another category is added to the add page number tool where it allows
for defining a 0 padded format. If left as 0, it will not added padded
0s and will be the current implementation.
-->

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [x] 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)
- [x] I have performed a self-review of my own code
- [x] 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)

- [x] 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.

---------

Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>

app/core/src/main/java/stirling/software/SPDF/controller/api/misc/PageNumbersController.java

@@ -52,9 +52,17 @@ public class PageNumbersController {
         int pageNumber = request.getStartingNumber();
         String pagesToNumber = request.getPagesToNumber();
         String customText = request.getCustomText();
+        int zeroPad = request.getZeroPad();
         float fontSize = request.getFontSize();
         String fontType = request.getFontType();
         String fontColor = request.getFontColor();
+        // compute padded number string where requested
+        String formatN;
+        if (zeroPad > 0) {
+            formatN = String.format("%%0%dd", Math.max(0, zeroPad));
+        } else {
+            formatN = "%d";
+        }
 
         Color color = Color.BLACK;
         if (fontColor != null && !fontColor.trim().isEmpty()) {
@@ -93,9 +101,10 @@ public class PageNumbersController {
                 PDPage page = document.getPage(i);
                 PDRectangle pageSize = page.getMediaBox();
 
+                String nFormatted = String.format(formatN, pageNumber);
                 String text =
                         customText
-                                .replace("{n}", String.valueOf(pageNumber))
+                                .replace("{n}", nFormatted)
                                 .replace("{total}", String.valueOf(document.getNumberOfPages()))
                                 .replace(
                                         "{filename}",

app/core/src/main/java/stirling/software/SPDF/model/api/misc/AddPageNumbersRequest.java

@@ -39,6 +39,13 @@ public class AddPageNumbersRequest extends PDFWithPageNums {
             requiredMode = RequiredMode.NOT_REQUIRED)
     private String fontColor;
 
+    @Schema(
+            description = "Zero-padding width for page numbers (Bates Stamping). Set to 0 to disable padding",
+            minimum = "0",
+            defaultValue = "0",
+            requiredMode = RequiredMode.NOT_REQUIRED)
+    private int zeroPad = 0;
+
     @Schema(
             description =
                     "Position: 1-9 representing positions on the page (1=top-left, 2=top-center,"