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Combine scanned documents into one PDF: A4, A3 and more

Published 2026-08-31 · How-to

You scanned a few pages but they came out in different sizes: an A4 contract, an A3 plan, a printed receipt. Instead of keeping them as separate files, here is how to combine them all into one tidy PDF, whatever their original dimensions.

Why mixed sizes are so common

Scanners and phone cameras do not guess the paper size before they digitise a page. An A3 plan shot in landscape, an A4 letter in portrait and a small receipt all produce pages of different width and height. Left as separate files they are clumsy to send and easy to lose. Gathering them into one PDF keeps everything together in reading order, ready to share or archive.

The fastest way to combine your scans

Open Images to PDF, drop all your scanned pages at once, and let the tool place each one on its own page. You do not need to resize anything first: the tool keeps each scan readable while building a single output file. Everything runs in your browser, so your documents never leave your device and there is no watermark added.

Keep each page readable despite different sizes

Pages in a combined file can have different dimensions, and readers do not mind as long as nothing is cut or shrunk into illegibility. The key is to let every page keep its natural proportions. Because the tool never forces a uniform size, an A3 plan stays as wide as it should be and a receipt stays small, just like the originals.

Order the pages before you merge

A few seconds spent ordering scans saves your recipient a lot of confusion. Put cover or summary pages first, then supporting documents in the order you would read them. If you later need to adjust, a combined file can be split again with PDF Splitter before you remerge the right pages.

Clean up before combining

Photographed scans often include tilt, shadows or useless borders. Straighter pages merge more cleanly, and the final file looks more professional. If a page came out sideways, fix its orientation first with PDF Rotate, then combine the corrected set.

Reduce the size of the final file

Several scanned pages can quickly become a heavy PDF, especially with photos. Before you send it, run the merged document through Compress PDF to bring the size down while keeping pages readable. The result is one neat, lightweight file ready for email or upload.

Combine it with already digital pages

Mixed documents are not only scans. Once you have built one PDF from your scans, you can merge it with a digital page using Merge PDF. The workflow follows a simple loop: assemble the scans, normalise the file, then add any digital pages you need.