Alternate & Mix PDF

Alternate & Mix PDF combines files by taking pages from each one in turn: page 1 of the first file, page 1 of the second file, page 2 of the first file and so on. It is the easiest way to join front and back sides that were scanned separately.

What is Alternate & Mix?

Alternate & Mix is a special way of combining PDF files. A normal merge places one file after another: all pages of the first file, then all pages of the second file. Mixing instead takes pages from each file in turn. With two files, the result is page 1 of file A, page 1 of file B, page 2 of file A, page 2 of file B, and so on. It sounds like a small difference, but it solves a very common and frustrating problem with scanners.

The double-sided scanning problem

Many home and office scanners have a document feeder that can only scan one side of the paper at a time. To scan a stack of double-sided pages, people scan all the front sides first, turn the stack over and scan all the back sides. You end up with two PDFs: one with pages 1, 3, 5 and 7, and another with pages 2, 4, 6 and 8. Worse, because the stack was turned over, the back sides usually come out in reverse order: 8, 6, 4, 2.

Putting these pages together by hand would mean dragging each page into place one by one. Alternate & Mix does it in one step. Add the front-side file first, add the back-side file second, choose to reverse the second file, and the tool produces a document in the correct reading order: 1, 2, 3, 4, 5, 6, 7, 8.

Options explained

• Reverse the second file. Turn this on when the back sides were scanned in reverse order. Turn it off if your scanner already produced them from first to last.
• Pages to take at a time. By default the tool takes one page from each file in turn. You can increase this number. For example, a value of 2 takes two pages from file A, then two from file B, which is useful for interleaving chapters or answer sheets.
• More than two files. You can add three or more files. The tool cycles through all of them in the order shown in the list.

What if the files have different lengths?

Real scans are not always perfect. If one file has more pages than the other, the tool keeps mixing until the shorter file runs out and then adds the remaining pages of the longer file at the end. Nothing is lost. If the result looks wrong, check that you did not scan a page twice, then use Organize PDF to make small corrections.

Other uses for mixing PDFs

• Translations. Combine an original document and its translation so each page is followed by its translated version.
• Questions and answers. Teachers can interleave question pages with answer or note pages.
• Before and after comparisons. Mix two versions of a design or report so each page is followed by its updated version, which makes reviews quicker.
• Forms and instructions. Place an instruction page in front of every form page.

Quality and privacy

Pages are copied exactly as they are from the original files, so text, images and page sizes stay the same. The mixing is done by your browser on your own device. Your scans, which often contain personal letters, bills and identity papers, are never uploaded to our servers.

Tips

• Name your scans clearly, such as front.pdf and back.pdf, so you add them in the right order.
• Check the first four pages of the result. If page 2 is wrong, switch the reverse option and try again.
• Large scanned files can be compressed afterwards with the Compress PDF tool.

How to use Alternate & Mix PDF

1. Select two or more PDF files and put them in the right order.
2. Choose whether to reverse the second file and how many pages to take at a time.
3. Click "Mix PDFs" and download the result.

Frequently asked questions

Why would I reverse the second file?

Many scanners feed the back sides in reverse order. Reversing the second file puts them back in the right order before mixing.

What if the files have a different number of pages?

The extra pages of the longer file are added at the end.

Can I mix more than two PDF files?

Yes. Add as many files as you need. The tool takes pages from each file in turn, in the order shown in the list.

Does mixing change the quality of my scans?

No. Pages are copied exactly as they are, so the resolution and file quality stay the same.

Is this tool really free?

Yes. All tools on this website are free to use, with no sign-up needed.

Are my files and data safe?

Yes. Everything is processed inside your own browser. Your files and text are not uploaded to our servers.

Does it work on mobile?

Yes. The tools work on modern phones, tablets and computers.