Feature/v2/navigate save prompt (#4586)

# Description of Changes

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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/src/services/pdfExportHelpers.ts

@@ -0,0 +1,46 @@
+import { PDFDocument } from '../types/pageEditor';
+import { pdfExportService } from './pdfExportService';
+import { FileId } from '../types/file';
+
+/**
+ * Export processed documents to File objects
+ * Handles both single documents and split documents (multiple PDFs)
+ */
+export async function exportProcessedDocumentsToFiles(
+  processedDocuments: PDFDocument | PDFDocument[],
+  sourceFiles: Map<FileId, File> | null,
+  exportFilename: string
+): Promise<File[]> {
+  console.log('exportProcessedDocumentsToFiles called with:', {
+    isArray: Array.isArray(processedDocuments),
+    numDocs: Array.isArray(processedDocuments) ? processedDocuments.length : 1,
+    hasSourceFiles: sourceFiles !== null,
+    sourceFilesSize: sourceFiles?.size
+  });
+
+  if (Array.isArray(processedDocuments)) {
+    // Multiple documents (splits)
+    const files: File[] = [];
+    const baseName = exportFilename.replace(/\.pdf$/i, '');
+
+    for (let i = 0; i < processedDocuments.length; i++) {
+      const doc = processedDocuments[i];
+      const partFilename = `${baseName}_part_${i + 1}.pdf`;
+
+      const result = sourceFiles
+        ? await pdfExportService.exportPDFMultiFile(doc, sourceFiles, [], { selectedOnly: false, filename: partFilename })
+        : await pdfExportService.exportPDF(doc, [], { selectedOnly: false, filename: partFilename });
+
+      files.push(new File([result.blob], result.filename, { type: 'application/pdf' }));
+    }
+
+    return files;
+  } else {
+    // Single document
+    const result = sourceFiles
+      ? await pdfExportService.exportPDFMultiFile(processedDocuments, sourceFiles, [], { selectedOnly: false, filename: exportFilename })
+      : await pdfExportService.exportPDF(processedDocuments, [], { selectedOnly: false, filename: exportFilename });
+
+    return [new File([result.blob], result.filename, { type: 'application/pdf' })];
+  }
+}