How to merge PDF files into one, on a phone or computer

To merge PDFs, open Merge PDF, add your files, drag them into the order you want and press Download. The combined file is built in your browser as you arrange the cards, so there is no separate "merge" step and nothing is uploaded.

Steps

1. Open Merge PDF and drop your PDFs onto the box, or tap it to choose files from your device. You need at least two files; until then the result bar says "Add one more file to merge".
2. Put the files in order. Drag a card to a new place, or use the arrows on each card. Pages follow the grid from left to right, so the first card's pages come first.
3. To sort quickly, use Name A to Z, Name Z to A or Reverse order under Order in the side panel.
4. Read the line under the files, for example "14 pages from 3 files". The merge is redone on your device every time the order changes.
5. Press Download to save merged.pdf. Where the browser can share files, a Share button beside it sends the same file to another app on the device.

Merging on a phone

The tool works in mobile browsers. On a phone, the card arrows are easier than dragging, especially with more than a handful of files. When you tap the box to add files, your phone offers its file picker, so PDFs saved from email or a messaging app can be picked from there.

Once the page has loaded, the merge itself needs no connection, so a weak signal does not interrupt it. Very large files use more memory, and an older phone may take a while on a big batch.

What the merged file keeps

Pages are copied as they are, without re-encoding, so text stays sharp and selectable and photos keep their original quality. That also means the merged file is roughly the size of all the inputs added together. If the result is too big for an email or a form, run it through Compress PDF afterwards.

Some other things carry over too:

Mixed page sizes

A letter-size contract and an A4 scan can live in one file, but the mix looks untidy when printed. To even them out, click a file's card to give it its own settings, then pick a page size such as A4. Its pages are scaled whole onto the new size. In the same settings you can turn every page of that file, or, with one file selected, click single pages to turn them a quarter right (Shift-click turns them left).

Hold Cmd or Ctrl to select several cards at once, and use Apply to all to make one file's settings the default for the rest.

Troubleshooting

A file shows "Has a password". The tool asks for it right in the page: type the password you were given and press Unlock. The file keeps its place in the order. This only works with a password you know; the tool does not guess passwords.

A card says "Not a readable PDF". The file is damaged or is not a PDF at all. Remove it with its cross, try Repair PDF on it, then add the repaired copy.

Files arrive in the wrong order. Names like scan 10 and scan 2 sort by number with Name A to Z, so numbered scans usually line up in one click.

You need to remove or move single pages, not whole files. Merge first, then open the result in Organize PDF pages to drag, turn or remove individual pages. The result bar also offers Open in PDF editor if you want to add text or a signature to the merged file.

Questions

Is there a limit on how many PDFs I can merge?

There is no fixed limit on files or pages. Everything runs on your device, so the practical ceiling is how much memory your browser can use.

Can I add a photo or a JPG to the merged PDF?

Yes. Add pictures to the same list as your PDFs and each one becomes a page. See how to combine a PDF and a JPG into one PDF.

Are my files uploaded?

No. The files are read and combined in your browser. Their contents and names are not sent to a server.

Will merging change the quality of my PDFs?

No. Pages are copied, not redrawn, so nothing is compressed along the way.