Merge PDF
Combine two or more PDF files into a single document, in the order you select them. Nothing is uploaded — the merge happens on your device.
- Click the file picker and select two or more PDF files (hold Ctrl on Windows or Cmd on a Mac to select several at once).
- Check the file list — your PDFs are merged in the order shown there.
- Click Merge PDFs. The combined file downloads to your device automatically.
Combining PDFs without sending them anywhere
Most free PDF mergers work by uploading your documents to a company's server, merging them there, and sending a file back. That is fine for a restaurant menu and a bad idea for a signed contract, a bank statement, a medical letter, or anything covered by a confidentiality agreement at work.
This tool takes the other approach. The merge runs in JavaScript inside your own browser tab using the open-source pdf-lib library. Your PDFs are read from your disk into your browser's memory, combined there, and written straight back out as a download. No copy of your document is ever transmitted, which also means there is no server-side copy to be retained, leaked, or subpoenaed later.
A useful side effect: because nothing is uploaded, speed depends on your computer rather than your internet connection. A 40 MB merge on a slow connection finishes just as fast as on a fast one, and works on a plane with the Wi-Fi off once the page has loaded.
Controlling the order pages end up in
Files are merged in the order they appear in the list under the file picker, which is the order your operating system hands them over — usually alphabetical by filename, not the order you clicked them. If the order matters, the reliable trick is to rename your files with a numeric prefix first: 01-cover.pdf, 02-report.pdf, 03-appendix.pdf. They will then merge in exactly that sequence every time.
What gets preserved, and what doesn't
Page content, embedded fonts, images and vector graphics all carry over exactly — this is a lossless copy of each page's content stream, not a re-render, so there is no quality loss no matter how many times you merge. Page dimensions are preserved per page too, so mixing A4 and Letter documents produces a PDF with mixed page sizes rather than stretching anything.
Two things do not survive a merge, and this is true of essentially every PDF merger: interactive form fields lose their values once two documents' field names collide, and existing digital signatures are invalidated. That second one is by design — a signature certifies a specific document, so any modification, including adding pages, necessarily breaks it. If you need a signed document combined with others, merge first and sign the result.
How many files can you merge at once?
There is no artificial cap — no "3 files per hour" limit, no account gate, no watermark on the output. The practical limit is your device's available memory, since every file is held in RAM during the merge. On a typical laptop, merging a few hundred megabytes of PDFs is comfortable. If you are combining something very large and the tab becomes unresponsive, merge in batches of ten or so and then merge those results together.