About Merge PDF Tool
Merge PDF is a professional, browser-based tool for combining multiple PDF documents into a single file. The application runs entirely client-side using PDF.js and pdf-lib libraries, ensuring complete data privacy as no files are uploaded to external servers.
This tool is designed for users who need to consolidate multiple PDF documents while maintaining full control over file sequencing, page orientation, and document organization without compromising security or requiring software installation.
Technical Capabilities
- ▸ Client-Side Processing: All PDF operations execute locally in your browser using WebAssembly and JavaScript libraries, with no server communication.
- ▸ Unlimited File Capacity: No restrictions on the number of PDFs or total file size, limited only by available system memory.
- ▸ Interactive Reordering: Drag-and-drop interface powered by Sortable.js for intuitive document sequencing before merge operation.
- ▸ Page Rotation: Individual page rotation controls (90° increments) with real-time preview updates.
- ▸ Thumbnail Generation: High-quality page previews rendered at configurable scale (default 1.2x) for accurate visual verification.
- ▸ Complete Privacy: Zero network requests during processing; files cleared from memory immediately after download.
How to Use
1 File Upload and Selection
Upload Methods Available:
- File Picker: Click "Select PDF Files" button to open system file browser. Supports multi-select (Ctrl+Click or Cmd+Click on multiple files).
- Drag & Drop: Drag PDF files directly from file explorer onto the upload zone. Multiple files can be dropped simultaneously.
- Keyboard Navigation: Tab to "Select PDF Files" button, press Enter to activate file picker dialog.
File Validation:
- Only PDF files (.pdf extension) are accepted; other formats will be rejected with error message.
- Each file is validated using PDF.js library before processing begins.
- Original file metadata (name, size) is preserved and displayed in the interface.
Technical Note: Files are loaded into browser memory as ArrayBuffers and never transmitted over network.
2 Document Organization and Preview
Thumbnail Preview System:
- Each uploaded PDF generates a canvas-based thumbnail showing the first page.
- Thumbnail rendering scale: 1.2x for clarity (configurable in browser console if needed).
- File information displayed: filename, page count, file size in KB/MB.
Available Control Options:
- Drag Handle (⋮⋮): Click and hold to reorder PDFs via drag-and-drop. Sortable.js library provides smooth reordering animation.
- Rotate Button (🔄): Click to rotate PDF pages in 90° increments clockwise. Rotation persists through merge operation.
- View Pages Button (👁️): Expands modal showing all pages within the PDF as thumbnails for verification.
- Remove Button (🗑️): Deletes PDF from merge queue without affecting browser cache or file system.
Reordering Workflow:
- Click drag handle (⋮⋮) on any PDF card.
- While holding mouse button, drag card vertically to desired position.
- Visual highlight indicates valid drop zones.
- Release mouse button to finalize new position.
- Final merge sequence will match displayed order from top to bottom.
Technical Note: Drag-drop uses Sortable.js v1.15.0 with disabled swap animation for immediate visual feedback.
3 Merge Execution
Merge Process:
- Click "Merge PDFs" button at bottom of document list.
- Processing stage indicator appears showing progress bar.
- pdf-lib creates new PDFDocument instance in memory.
- Pages from each PDF are copied sequentially in displayed order.
- Rotation transformations applied per individual page settings.
- Metadata preserved from source documents where applicable.
Processing Stages:
- Parse source PDF binary data using pdf-lib
- Extract page objects from each document
- Apply rotation matrices to designated pages
- Copy pages to new PDF document maintaining original quality
- Serialize final PDF to Uint8Array
- Generate Blob for browser download
Performance: Merging speed depends on total page count and system resources. Typical performance: ~50-100 pages per second on modern hardware.
4 Download and Cleanup
Download Process:
- Upon completion, "Download Merged PDF" button becomes active.
- Click button to trigger browser's native download mechanism.
- Default filename: "merged.pdf" (can be renamed before saving via browser dialog).
- File size and page count displayed for verification.
Post-Download Options:
- "Merge Another PDF" button: Resets application state and clears all data from memory.
- "Add More Files" option: Allows adding additional PDFs to existing queue for subsequent merge operations.
Privacy and Data Management:
- All file data cleared from JavaScript memory upon page reload or "Merge Another PDF" action.
- No cookies, localStorage, or IndexedDB used for file storage.
- Browser cache contains only thumbnail render canvases (automatically cleared on page close).
Privacy Guarantee: Zero network activity during entire workflow. Verify via browser DevTools Network tab.
Professional Use Cases
Business Documentation
Consolidate invoices, purchase orders, contracts, and financial statements into comprehensive business packages for archival or client delivery.
Academic Publishing
Merge dissertation chapters, appendices, references, and supplementary materials into final thesis submission documents.
Legal Case Management
Combine evidence documents, exhibits, affidavits, and case filings into organized legal bundles for court submission or discovery production.
Medical Records Compilation
Aggregate patient charts, lab results, imaging reports, and treatment histories into comprehensive electronic health record packages for continuity of care or insurance claims.