Merge PDF Files
Combine multiple PDFs into one document, in your chosen order — 100% in-browser.
About This Tool & Technical Logic
Combines any number of PDFs into a single document. Files are processed with pdf-lib entirely in your browser — no upload, no size anxiety, no watermark — which also makes it faster than server tools for big files.
Page order follows the file list; drag to reorder before merging. Each source keeps its own page size and orientation in the merged output, exactly as a print shop would collate them.
PDFDocument.create() → for each file: copyPages(all) → addPage() — object streams preserved, quality lossless.
How to Use — Step by Step
- 1
Add your PDFs
Click or drop multiple files. The list shows page counts so you can verify everything loaded.
- 2
Set the order
Use the arrows to move files — top-to-bottom order becomes page order in the output.
- 3
Merge and download
The output downloads instantly with all form fields and annotations intact.
Frequently Asked Questions
Only your device's memory — merging hundreds of megabytes locally is normal. Since nothing uploads, speed depends on your CPU, not your connection.