How to merge PDF files

Updated October 25, 2026

Combine several PDFs into one file, choose the order, and save it, without your files leaving your device.

Why merge PDFs locally

Merging is one of the most common PDF jobs: a contract and its appendices, a stack of scanned receipts for an expense report, or chapters exported separately from a word processor. Most online "merge PDF" sites ask you to upload every file to their server, process them there and send the result back. That works, but it means copies of your documents sit on someone else's computer, at least for a while. PDF One merges files inside your browser instead, so the pages never travel anywhere.

Step by step

  1. Open the PDF One editor. It loads once and then works offline.
  2. Click Open (or drag your files onto the page) and pick all the PDFs you want to combine. You can select several at once.
  3. Each file appears in the Files list on the left. Drag the files up or down until they are in the order you want.
  4. Tick the files you want to combine and choose Merge files. PDF One builds a new document with the pages of each file one after another.
  5. Check the result in the Pages view. You can still drag single pages to a new position or delete pages you don't need.
  6. Click Save a copy to write the merged PDF to your device. Give it a clear file name so you can find it later.

Interleaving scanned pages

If you scanned a double-sided document on a single-sided scanner, you usually end up with two files: all the front sides and all the back sides (often in reverse order). The merge dialog has an Interleave pages option that alternates pages from the two files (front 1, back 1, front 2, back 2 and so on), which saves you from reordering dozens of pages by hand.

Tips for a clean result

  • Rotate sideways pages before you save, so the merged file reads the right way up on every device.
  • Remove blank pages left over from scanning; they make the file longer and larger for no reason.
  • Keep the original files until you have checked the merged copy. PDF One never deletes or changes your originals unless you save over them.
  • Very large merges (hundreds of pages) use your device's memory. On an older phone, merging in two smaller batches is faster.

Is it really private?

Yes. The editor page is protected by a strict Content Security Policy that tells your browser to block any connection to another server, so the files you merge have nowhere to go. You can confirm it yourself: turn off Wi-Fi after the editor has loaded and merging still works. Read more in why offline PDF editing is safer.

Open the PDF One editor

More guides