About the PDF Interleave Merger
Many document scanners without a double-sided feature make you scan the front sides first, flip the stack and scan the backs. You then end up with two PDFs: one with the odd pages and one with the even pages, often with the backs in reverse order. This tool merges them back into one file by taking one page from each in turn. Choose which file starts, and tick the option to reverse the second file when the backs were scanned from last to first. If one file is longer, its extra pages are added at the end. It is also useful for any case where two documents should be woven together, such as a document and its translation. The work happens in your browser.
Updated October 2026
How to use the PDF Interleave Merger
- 1Pick file A, for example the front sides.
- 2Pick file B, for example the back sides.
- 3Tick Reverse the pages of file B if the backs were scanned in reverse order.
- 4Choose which file supplies the first page.
- 5Press Merge alternately and download the result.
The usual double-sided scanning workflow
Place the pages in the scanner feeder face up, scan them, and save the file as fronts. Take the stack out, turn it over without changing the order, put it back and scan again for the backs. Because the stack was flipped, the back of the last page comes first. That is why the second file usually needs to be reversed.
Check the result by looking at the first few pages. Page 1 should be a front, page 2 its back, page 3 the next front. If page 2 looks like the back of the wrong sheet, run the merge again and change the reverse option.
Other uses
- Weave a document with its translation, page by page.
- Join a slide deck with a blank note page after each slide.
- Put an answer sheet after each question sheet.
- Combine two scanned halves of a book.
- Add a separator page between every page of a file.
Related tools
For a normal join of several files, use Merge PDF, and to move pages afterwards use Rearrange PDF Pages. Straighten scanned pages with Rotate PDF, shrink the result with Compress PDF and make the scans searchable with PDF OCR. Scanning at 200 to 300 dpi keeps a good balance between quality and size.
Features
- Alternates one page from each file
- Reverse option for back sides
- Choose which file starts
- Extra pages of the longer file go last
- Pages are copied without changes
- No upload, works offline
Frequently asked questions
How do I merge odd and even pages?
Put the odd pages in file A and the even pages in file B, keep Start with File A, and press Merge. If the even pages are in reverse order, also tick the reverse option.
When do I need to reverse the second file?
When you scanned the fronts first, then flipped the whole stack and scanned the backs. The first back scanned is the last page of the document, so the backs come out in reverse order.
What if the files have different page counts?
The pages are woven in turn until the shorter file runs out. The remaining pages of the longer file are added at the end, and the tool tells you.
Does it change the page size?
No. Each page keeps its own size, rotation and content.
Can I merge more than two files?
Not at once. Merge two, then use the result as file A in another run. For a plain join of many files, use the ordinary merge tool.
Does the order of A and B matter?
Yes. The first page of the result comes from the file you choose, and the rest alternate after it.
Is my scan uploaded?
No. Both files are read and merged in your browser.