PDF Merge
Combine multiple PDF files into one final document in your browser.
Advanced — optimized output
What is PDF Merge?
PDF Merge combines multiple PDF files into a single document. Whether you're assembling a report from separate chapters, merging scanned documents, or consolidating invoices and receipts, this tool lets you create one cohesive PDF without uploading files to any server. All processing runs client-side in your browser using pdf-lib—your documents never leave your device.
Real-world use cases include combining contract drafts from multiple parties, merging presentation slides with handouts, creating a single PDF from multiple scan batches, and assembling project documentation. You can drag and drop files to reorder them before merging, and the stats panel shows total page count and merged file size. The optional Optimize output size setting in Advanced reduces file size while preserving content.
How to Use PDF Merge
- Click the dropzone or drag and drop two or more PDF files. Up to 50 MB per file.
- Reorder files using the up/down arrows or by drag-and-drop if supported. The order determines page order in the final output.
- Open Advanced and enable Optimize output size for smaller merged files.
- Click Merge PDFs to combine them. Processing runs in your browser.
- Click Download PDF when the merge completes. Stats show input file count, total pages, and merged size.
Tips & Best Practices
Add files in the order you want them to appear—merge order is file order. Use the up/down buttons to move files without re-uploading. Enable Optimize output size to reduce file size via object stream compression (lossless). Press Ctrl+Enter to merge and Escape to clear. If the merged PDF is still too large, run it through our PDF Compress tool. Need to extract specific pages instead? Use PDF Split.
When to Use This Tool
Use PDF Merge when combining reports, contracts, scanned documents, or any multi-file PDF workflow. Pair it with PDF Split to extract pages before merging, or PDF Compress to reduce the size of the merged result. All ToolCrux PDF tools run client-side—your documents stay private and secure.
Frequently Asked Questions
Is PDF merge safe? Are my files uploaded?
Yes. PDF Merge uses 100% client-side processing. Your files never leave your browser—there is no upload to any server. All merging happens locally using pdf-lib in JavaScript.
Is there a limit on the number of PDFs?
No hard limit. The number of PDFs you can merge depends on your browser's memory. For very large batches, merge in smaller groups if needed.
How many PDFs can I merge at once?
You can merge as many PDF files as your browser memory allows. Select two or more files, drag to reorder if needed, then click Merge PDFs. The combined document is generated instantly.
Can I reorder PDFs before merging?
Yes. Drag and drop to reorder files in the list. The order of files determines the page order in the merged PDF.
Are my PDFs uploaded to a server?
No. Everything runs in your browser. Your PDFs are processed locally and never leave your device.
What if I need to extract or split pages instead?
Use our PDF Split tool to extract specific page ranges from a PDF. For compressing large merged files, try our PDF Compress tool. Both run client-side with no upload.
Does PDF Merge work offline?
After the page loads, yes. The PDF engine (pdf-lib) runs entirely in your browser. Once loaded, you can merge PDFs without an internet connection.