Combine any number of PDFs into one, in order, entirely in your browser
Click or drag PDF files here (multiple at once)
| Method | Files Leave Your Device? | Cost | Best For |
|---|---|---|---|
| This tool (in-browser) | No | Free | Quick merges of any size; confidential documents |
| Adobe Acrobat (desktop) | No | Paid subscription | Frequent professional use, bookmarks, portfolios |
| macOS Preview | No | Free (built-in) | Mac users — drag thumbnails in the sidebar |
| qpdf (command line) | No | Free, open source | Scripted/repeated merges: qpdf --empty --pages a.pdf b.pdf -- out.pdf |
| pdftk (command line) | No | Free | Linux/Windows scripting: pdftk a.pdf b.pdf cat output out.pdf |
| Online upload sites | Yes — files go to their servers | Freemium | Only when nothing local is available; check their retention policy |
Windows has no built-in PDF merger (Print to PDF can't combine), which is why the upload sites dominate the search results. A browser tool gives you the same one-click convenience with the privacy of a desktop app.
A PDF file is a container of page objects, fonts, and images referenced through a cross-reference table. Merging builds a fresh document and copies each input's page tree into it, in order. Because pages are copied rather than re-rendered, nothing is recompressed: text stays selectable, vector graphics stay vector, embedded fonts stay embedded, and a scanned page remains the same scan. The output file is roughly the sum of the input sizes — not exactly, because the new document writes its own cross-reference structures and can deduplicate objects the inputs shared.
Merging three files — a 12-page scanned contract (4.2 MB), an 8-page report (1.1 MB), and a 5-page appendix (300 KB) — produces one 25-page PDF: contract pages 1–12, report pages 13–20, appendix pages 21–25. Reordering the list before merging changes that page map: putting the report first gives 1–8, contract 9–20, appendix 21–25. Total output lands around 5.6 MB, slightly under the 5.6 MB sum of inputs once the new file's tables and any duplicate font objects are accounted for. The equivalent shell command is qpdf --empty --pages contract.pdf report.pdf appendix.pdf -- merged.pdf.
This page loads the pdf-lib engine (MIT-licensed, maintained as @cantoo/pdf-lib) from a CDN and then does all work locally through the browser's FileReader and Blob APIs. Open your browser's network tab while merging: you'll see the page assets load once, then zero requests as you merge. That's the difference between this and an upload-based service, where your M&A deck or medical record sits on someone else's disk for some retention period.
Yes. The merge runs 100% in your browser using a local copy of the open-source pdf-lib engine. Your files are read from disk into memory, combined, and handed back as a download — they are never uploaded to any server, so there is nothing to leak, store, or expire. You can even disconnect from the internet after the page loads and it still works.
Each file appears as a row in the list; drag rows to reorder them (or use the up/down buttons on touch screens). The merged PDF contains all pages of the first file, then all pages of the second, and so on. If you need pages 1-3 of one file only, split or extract first, then merge the pieces.
No. Pages are copied byte-for-byte into the new document — text stays selectable vector text, images keep their original resolution, and fonts are embedded as they were. The output size is roughly the sum of the inputs; small differences come from the new cross-reference tables and shared objects being deduplicated, not from recompression.
Not while they are encrypted. An owner-password-protected file must be decrypted first — open it in a viewer that has the password and re-save or print-to-PDF an unlocked copy, then merge that. The tool reports any file it cannot read instead of silently skipping it.
No. A digital signature covers the exact bytes of the signed document, so any merge — by any tool, including Acrobat — breaks the signature's integrity over the combined file. Signed pages still display their visual signature panels, but the cryptographic verification no longer passes. Get signatures after merging, not before.
No artificial limit. Because the merge happens in your browser's memory, the practical ceiling is your device's RAM — a typical laptop handles hundreds of megabytes comfortably. Upload-based services impose free-tier caps of roughly 25-100 MB per file; local merging has no such tier because there is no upload at all.