Online PDF Merger
Merge multiple PDF files into one for free. Drag to reorder, secure local processing.
How to Use
Select file
Start process
Local processing
Download result
Complete PDF Merge Guide
How the merge works
Allin PDF merges files entirely in your browser — the PDFs you select are never uploaded to a server. Add 2 to 20 PDF files, drag the list to set their order (on desktop), then click Merge to get one PDF in that order, named "<first file>_merged.pdf". Pages are copied as-is without re-compression, so image quality and page sizes stay exactly the same; bookmarks (outlines) from the source files are not carried over. Free accounts can merge files up to 5MB each, Pro up to 50MB. Password-protected PDFs must be unlocked before merging.
Merging on Windows, Mac and iPhone
Windows has no built-in way to merge PDFs, so just open Allin PDF in Chrome or Edge — no software to install. On a Mac, Preview can merge files: open the first PDF, show the thumbnail sidebar and drag the other PDFs into it; for many files or frequent reordering, the browser tool is quicker. On iPhone, select several PDFs in the Files app and choose "Create PDF", or use the Allin PDF iOS app. Mobile browsers may not support drag-to-reorder, so select the files in the order you want.
Tips and common problems
"This PDF is password-protected": remove the open password first with the Unlock PDF tool in the web app (runs in your browser; you need the current password). File too large: the free limit is 5MB per file — compress the PDF first. Merged file is big: merging does not compress, so the output is roughly the sum of the inputs; compress it afterwards if you need to email it. Only need some pages: split the PDF first, then merge the parts you need.
Processing Results
Technical Specifications
Feature Comparison
| Feature | Allin PDF | Other Tools |
|---|---|---|
| File upload | Not needed — merged in your browser | Many online tools upload files to their servers |
| Files per merge | Up to 20 (free) | Varies by service and plan |
| Sign-up | Not required | Varies by service |
Key Facts
Merge up to 20 PDFs at once and drag files to set their order.
Merging runs locally in your browser (Web Worker) — files are never uploaded to a server.
Pages are copied as-is without re-compression, so quality and page size stay the same; source bookmarks (outlines) are not carried into the merged file.
Privacy Protection
This tool processes your files in your browser: they are not uploaded to a server, and no sign-up or login is needed.
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FAQ
How many PDFs can I merge at once?
Up to 20 PDFs per merge. Each file can be up to 5MB on the free plan and 50MB on Pro. To combine more than 20, merge them in batches and then merge the results.
How do I merge two PDFs into one?
Open the merge tool, select both PDFs, make sure the one that should come first is at the top of the list, then click Merge and download the result. It takes a few seconds and no account is needed.
Can I change the order before merging?
Yes. On a computer, drag the files in the list to reorder them; the merged PDF follows the list from top to bottom. Some mobile browsers do not support dragging, so on a phone select the files in the order you want, or use the iOS app.
Are my files uploaded when merging?
No. Merging runs in your browser using pdf-lib in a Web Worker. Your PDFs stay on your device.
Are bookmarks and quality preserved?
Quality is preserved: pages are copied without re-compression, so text, images and page sizes are unchanged. Bookmarks (outlines) from the source files are not carried into the merged PDF.
Can I merge password-protected PDFs?
Not directly. Remove the password first with the Unlock PDF tool in the Allin PDF web app (it runs in your browser; you need the current password), then merge. You can add a password to the merged file afterwards with PDF Encrypt.
Process Documents Anywhere
Download the Allin PDF iOS app. Its local tools also work offline.