Feature/v2/pageeditor improved (#4289)

# Description of Changes

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

Rewrite of page editor to make it work properly.  
Added page breaks
Added merged file support
Added "insert file" support
Slight Ux improvements

Closes #(issue_number)
-->

---

## 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.

---------

Co-authored-by: Anthony Stirling <[email protected]>

frontend/src/services/thumbnailGenerationService.ts

@@ -40,7 +40,7 @@ export class ThumbnailGenerationService {
   private pdfDocumentCache = new Map<string, CachedPDFDocument>();
   private maxPdfCacheSize = 10; // Keep up to 10 PDF documents cached
 
-  constructor(private maxWorkers: number = 3) {
+  constructor(private maxWorkers: number = 10) {
     // PDF rendering requires DOM access, so we use optimized main thread processing
   }
 
@@ -207,6 +207,9 @@ export class ThumbnailGenerationService {
     
     // Release reference to PDF document (don't destroy - keep in cache)
     this.releasePDFDocument(fileId);
+    
+    this.cleanupCompletedDocument(fileId);
+    
     return allResults;
   }
 
@@ -289,6 +292,18 @@ export class ThumbnailGenerationService {
     }
   }
 
+  /**
+   * Clean up a PDF document from cache when thumbnail generation is complete
+   * This frees up workers faster for better performance
+   */
+  cleanupCompletedDocument(fileId: string): void {
+    const cached = this.pdfDocumentCache.get(fileId);
+    if (cached && cached.refCount <= 0) {
+      pdfWorkerManager.destroyDocument(cached.pdf);
+      this.pdfDocumentCache.delete(fileId);
+    }
+  }
+
   destroy(): void {
     this.clearCache();
     this.clearPDFCache();