How to merge PDFs without uploading them anywhere

Most online PDF tools work by uploading your files to a server, processing them there and sending the result back. That is fine for a flyer. It feels different for a signed lease, a tax form or medical records. You can merge PDFs without sending them anywhere: the work can happen inside your web browser, on your own computer.

How in-browser PDF tools work

Modern browsers can run compiled code at close to native speed using a technology called WebAssembly. Our Merge PDF tool uses it to run a full PDF engine in the browser tab:

• When you add files, the browser reads them from your disk into the page's memory.
• The PDF engine combines them in a background thread on your computer.
• The merged PDF is saved straight back to your Downloads folder.

At no point is the content of your files sent over the internet. The page only downloads the engine itself, once, the first time you use it.

Merge PDFs step by step

1. Open Merge PDF and drop in your PDFs, or select Choose files.
2. Drag the files into the order you want. Each file shows its page count and a thumbnail of the first page.
3. Select Merge PDF.
4. Download the combined file.

Links, bookmarks and fillable form fields may not all survive merging. Keep your originals and check these features in the merged PDF before sharing it. The free plan merges up to 10 files at a time; Pro merges up to 100.

Need to drop a page or fix a sideways scan before or after merging? Use Organize PDF to rotate, delete and reorder pages.

Check for yourself that nothing is uploaded

You don't have to take our word for it. Two quick ways to check:

• Go offline. Add your files to the merge tool first, so the engine is loaded. Then turn off Wi-Fi or unplug the network cable and select Merge PDF. The merge still works, because it never needed the network.
• Watch the network. In Chrome or Edge, press F12 and open the Network tab before you add files. You will see the page load its own scripts and the engine, but no request carrying your PDFs.

Things to know

• Password-protected PDFs can't be merged yet. Open the file in the app that created it, save a copy without the password, and merge that copy.
• Very large files are limited by your computer's memory rather than a server's. If a merge fails, try merging fewer files at a time.
• Scanned pages are merged as they are. If some pages are sideways, rotate them with Rotate PDF.