PDF Merger Documentation

Overview

The PDF Merger is a powerful, privacy-focused tool that allows you to combine multiple PDF files into a single document. All processing happens entirely in your browser, ensuring your files remain private and secure.

Key Features

🔒 Complete Privacy

100% Client-Side Processing: All PDF operations happen in your browser using JavaScript
No Server Uploads: Your files never leave your device
Zero Data Collection: We don't store, analyze, or transmit your PDFs
Offline Capable: Works without an internet connection once the page is loaded

📁 Multiple File Support

Upload multiple PDF files at once
Support for PDFs of any size (limited only by browser memory)
Automatic page count detection for each file
File size display for easy reference

🔄 Flexible Reordering

Drag & Drop: Click and drag files to reorder them
Arrow Buttons: Use up/down arrows for precise positioning
Real-Time Preview: See the final order before merging
Visual Feedback: Clear numbering shows merge sequence

⚡ Fast Processing

Efficient PDF parsing with progress indicators
Real-time progress bar during file uploads
Quick merging with visual feedback
Instant download when complete

How to Use

Step 1: Upload PDF Files

Click the upload area or drag PDF files onto it
Select multiple PDF files from your device
Wait for the files to be processed (progress bar shows status)
Each file's page count and size will be displayed

Tip: You can upload files in any order - you'll be able to rearrange them in the next step.

Step 2: Arrange the Order

Choose your preferred method to organize the PDFs:

Method 1: Drag & Drop (Recommended)

Click and hold the grip icon (⋮⋮) or anywhere on a file card
Drag the file to your desired position
Release to drop it in the new location
The numbers will automatically update to show the new sequence

Method 2: Arrow Buttons

Click the up arrow (↑) to move a file one position higher
Click the down arrow (↓) to move a file one position lower
Continue until files are in your desired order

Important: The merged PDF will combine files from top to bottom in the exact order shown.

Step 3: Remove Unwanted Files (Optional)

Click the X button on any file to remove it from the list
Removed files won't be included in the final merged PDF
You can remove files at any time before merging

Step 4: Merge PDFs

Ensure you have at least 2 PDF files in the list
Verify the order is correct
Click the "Merge PDFs" button
Wait for the merging process to complete (progress indicator shows status)
A success message will appear when done

Step 5: Download Merged PDF

Once merging is complete, the "Download Merged PDF" button appears
Click it to save the merged PDF to your device
The file will be named merged.pdf by default
You can rename it after downloading

Use Cases

Business & Professional

Contract Consolidation

Combine multiple contract pages into one document
Merge signed agreements with their exhibits
Create complete proposal packages

Report Assembly

Combine sections written by different team members
Merge appendices with main report
Create comprehensive project documentation

Invoice Batching

Combine multiple invoices into one PDF
Merge receipts for expense reports
Create monthly billing packages

Education & Academia

Assignment Compilation

Combine multiple homework files into one submission
Merge research papers with supplementary materials
Create complete thesis documents

Study Material Organization

Combine lecture slides from different sessions
Merge study guides into comprehensive resources
Create organized course material packages

Personal Use

Document Organization

Combine scanned documents into one file
Merge bank statements by year
Create organized personal records

Travel Planning

Combine flight confirmations, hotel bookings, and itineraries
Merge travel documents into one package
Create complete trip documentation

Family Archives

Combine family documents
Merge scanned photos and certificates
Create organized family history files

Technical Details

Supported Formats

Input: PDF files only (.pdf extension)
Output: Standard PDF 1.x format
Compatibility: Works with all standard PDF versions

File Processing

Library: Uses pdf-lib for PDF manipulation
Page Extraction: Copies all pages from each source PDF
Metadata: Preserves individual PDF metadata where possible
Compression: Maintains original compression settings

Browser Requirements

Modern Browsers: Chrome 90+, Firefox 88+, Safari 14+, Edge 90+
JavaScript: Must be enabled
Memory: Depends on total size of PDFs being merged
File System API: Required for downloading merged file

Performance Considerations

Large Files: May take longer to process (10+ MB PDFs)
Many Files: Upload time increases with file count
Total Size: Browser memory limits apply (typically 1-2 GB)
Page Count: More pages = longer merge time

Tips & Best Practices

Organizing Files

✅ Do:

Name your PDFs descriptively before uploading
Verify page counts match your expectations
Double-check the order before merging
Keep related documents in logical sequence

❌ Don't:

Mix sensitive and non-sensitive documents without verification
Merge without checking for duplicate pages
Forget to remove test or draft files

Optimal Workflow

Prepare Files First: Organize and name PDFs on your computer before uploading
Upload in Batches: If you have many files, upload them in logical groups
Review Before Merging: Always check the final order and file list
Test with Small Files: Try merging 2-3 small PDFs first to understand the process
Save Originals: Keep your original PDF files as backups

Performance Tips

Close Other Tabs: Free up browser memory for large merges
Smaller Batches: Merge 5-10 files at a time for better performance
Optimize PDFs: Compress large PDFs before merging if possible
Modern Browser: Use the latest browser version for best performance

Troubleshooting

Upload Issues

Problem: Files won't upload

Solution: Ensure files are valid PDFs (not images or other formats)
Check: File extension should be .pdf
Try: Re-save the file as PDF if it was converted from another format

Problem: "Not a PDF file" error

Solution: The file may be corrupted or in a different format
Check: Open the file in a PDF reader to verify it's valid
Try: Re-export or re-save the document as PDF

Problem: Upload is very slow

Solution: Large files take time to read and process
Expected: Files over 10 MB may take several seconds per file
Patience: Wait for the progress bar to complete

Reordering Issues

Problem: Drag and drop doesn't work

Solution: Ensure JavaScript is enabled in your browser
Alternative: Use the up/down arrow buttons instead
Try: Refresh the page and try again

Problem: Files jump to wrong position

Solution: Drag more slowly and wait for the drop zone to highlight
Try: Use arrow buttons for precise positioning

Merging Issues

Problem: "Failed to merge PDFs" error

Solution: One or more PDFs may be corrupted or password-protected
Check: Remove files one by one to identify the problematic PDF
Try: Ensure all PDFs can be opened normally before merging

Problem: Merge takes too long

Solution: Large PDFs or many pages take time to process
Expected: 100+ page documents may take 30+ seconds
Wait: Don't close the browser tab during merging

Problem: Browser becomes unresponsive

Solution: Total file size may exceed browser memory
Reduce: Try merging fewer or smaller PDFs
Close: Close other tabs to free up memory

Download Issues

Problem: Download button doesn't work

Solution: Ensure your browser allows file downloads
Check: Browser settings may be blocking downloads
Try: Right-click the button and "Save Link As"

Problem: Downloaded file is corrupted

Solution: Merge process may have been interrupted
Try: Merge again and ensure the process completes fully
Verify: Don't close the tab until download is complete

Privacy & Security

What We Do

✅ Process PDFs entirely in your browser
✅ Use open-source libraries (pdf-lib)
✅ Delete merged PDFs from memory when you leave the page
✅ Provide complete transparency about our process

What We Don't Do

❌ Upload your files to any server
❌ Store any PDF data
❌ Track or analyze your documents
❌ Share your files with third parties
❌ Require account creation or login

Security Recommendations

Use this tool on a secure, trusted device
Don't merge highly sensitive documents on public computers
Clear your browser cache after working with sensitive PDFs
Keep your browser updated for the latest security patches

Frequently Asked Questions

General Questions

Q: Is there a file size limit?
A: There's no artificial limit, but your browser's memory capacity determines the practical maximum. Most browsers can handle files up to 1-2 GB total.

Q: How many PDFs can I merge at once?
A: There's no hard limit, but performance degrades with many large files. We recommend merging 10-20 files at a time for optimal performance.

Q: Can I merge password-protected PDFs?
A: No, password-protected PDFs must be unlocked before merging. Remove the password using another tool first.

Q: Will the merged PDF retain hyperlinks and bookmarks?
A: Basic hyperlinks within pages are preserved, but bookmarks and document-level links may not transfer. This is a limitation of the PDF format when merging.

Q: Can I add blank pages between PDFs?
A: Currently, no. The tool merges PDFs directly without adding separators. You can create a blank PDF and upload it between other files as a workaround.

Technical Questions

Q: What happens if I close the page during merging?
A: The process will stop, and you'll need to start over. Your original files remain safe on your device.

Q: Does this work offline?
A: Once the page is loaded, most functionality works offline since processing happens in your browser. However, you need an initial internet connection to load the tool.

Q: Can I use this on mobile devices?
A: Yes, it works on modern mobile browsers, but performance may be slower for large files due to limited mobile device memory.

Q: Why does it take time to upload files?
A: The tool is reading each PDF to extract page counts and validate the files. This happens locally in your browser, not uploading to a server.

Q: What if I accidentally merged files in the wrong order?
A: You'll need to merge them again in the correct order. The tool doesn't modify your original files, so they remain intact.

Privacy Questions

Q: Are my PDFs stored anywhere?
A: No. Processing happens entirely in your browser's memory, and data is cleared when you close the tab.

Q: Can I trust this tool with confidential documents?
A: Yes, for client-side processing. However, always follow your organization's security policies regarding document handling.

Q: Do you collect any data about the PDFs I merge?
A: No. We don't have access to your files, their contents, or any metadata. Everything stays on your device.

Q: Is my merge history saved?
A: No. There's no history or cache of merged documents. Each session is completely independent.

Limitations

Current Limitations

Cannot merge password-protected PDFs
Cannot add page numbers to merged document
Cannot add table of contents or bookmarks
Cannot split or extract pages (use a PDF splitter tool)
Cannot edit PDF content before merging
Limited by browser memory for very large files

Planned Features

Support for adding blank separator pages
Option to add page numbers to merged PDF
Preview thumbnails of PDF pages
Remember merge order for repeated tasks
Batch export with custom filenames

Browser Compatibility

Fully Supported

✅ Google Chrome 90+ (Windows, macOS, Linux)
✅ Microsoft Edge 90+ (Windows, macOS)
✅ Mozilla Firefox 88+ (Windows, macOS, Linux)
✅ Safari 14+ (macOS, iOS)
✅ Opera 76+ (Windows, macOS, Linux)

Mobile Support

✅ Chrome Mobile (Android 10+)
✅ Safari Mobile (iOS 14+)
⚠️ Firefox Mobile (Limited performance)

Not Supported

❌ Internet Explorer (any version)
❌ Very old browser versions
❌ Browsers with JavaScript disabled

Related Tools

Explore other PDF and document tools on AppsFactory:

PDF Compressor - Reduce PDF file size
PDF Splitter - Extract pages from PDFs
Image to PDF - Convert images to PDF format
PDF to Images - Extract images from PDFs

Credits & Technology

Built With

pdf-lib - Modern PDF manipulation library
React - User interface framework
Next.js - Web application framework
Tailwind CSS - Styling and design
Lucide Icons - Beautiful icon system

Open Source

This tool is built using open-source technologies and respects your privacy by design.

Support & Feedback

Having issues or suggestions? We'd love to hear from you:

Report bugs or request features through our feedback system
Check for updates and new features regularly
Share this tool with others who might find it useful

Last Updated: November 2025
Version: 1.0.0
License: Free to use

AppsFactory - Privacy-first tools for everyone. Created by Gorav Singal.

PDF Merger

Privacy & Security - 100% Client-Side Processing