Interleave Two PDFs
Choose a file with the front sides and another with the back sides. The tool alternates their pages into one PDF, and can read the second file from the end, as a duplex scan done in two passes needs.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose the first file (A) and then the second file (B).
- Tick the reverse option if B holds the back sides scanned in the opposite order.
- Press Interleave and download. The file is named
interleaved.pdf.
How it works
The tool copies all pages of both files into a new PDF with pdf-lib and puts them in the order A1, B1, A2, B2 and so on. With the reverse option, B is read from its last page to its first.
Example
A has pages a1, a2, a3 and B has b1, b2, b3. Plain: a1 b1 a2 b2 a3 b3. With B reversed: a1 b3 a2 b2 a3 b1, which is right when b3 is the back of a1.
Tips
- If the result looks wrong, run it again with the reverse option switched.
- To combine files one after the other instead, use the Merge PDF tool.
Frequently asked questions
What is a two-pass duplex scan?
A scanner with a single-sided feeder scans all the front sides, then you turn the stack over and scan the backs. The backs come out last page first, so tick the reverse option to get the pages in the right order.
What if the files have different lengths?
The pages are alternated as long as both have pages, then the remaining pages of the longer file follow. The tool shows a note when the page counts differ.
Does it matter which file I put first?
Yes. The first file supplies pages 1, 3, 5 and so on of the result, the second file pages 2, 4, 6. For a scan, the fronts go first.
Are the page sizes kept?
Yes. Every page is copied as it is, so mixed sizes and rotations stay as they were.
Why does it refuse my file?
Password-protected and damaged PDFs cannot be processed. Each file can be up to 100 MB.