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ORGANIZE
Combine a PDF of front sides and a PDF of back sides into one file, in the right order.
QUICK ANSWER
To interleave two PDFs, add the PDF with the front pages, then the PDF with the back pages. StackPDF weaves them together as front 1, back 1, front 2, back 2, and you download one file. It runs in your browser, so neither file is uploaded.
Updated 31 October 2026 · Written by the StackPDF teamUpdated 31 October 2026 · StackPDF team
Two PDFs: front sides first, then back sides. They stay in this browser.Two PDFs: front sides first, then back sides. They stay in this browser.
PDF files · Runs in your browser
QUICK ANSWER
To interleave two PDFs, add the PDF with the front pages, then the PDF with the back pages. StackPDF weaves them together as front 1, back 1, front 2, back 2, and you download one file. It runs in your browser, so neither file is uploaded.
Updated 31 October 2026 · Written by the StackPDF teamUpdated 31 October 2026 · StackPDF team
HOW TO
First the PDF of front sides, then the PDF of back sides. Swap them if they’re the wrong way round.
The preview shows F1, B1, F2, B2. Turn on reverse if the backs were scanned last page first.
Every page is in reading order in a single file.
GOOD TO KNOW
Scan the fronts, flip the stack, scan the backs, then interleave the two files.
| SITUATION | WHAT TO DO | RESULT |
|---|---|---|
| Backs scanned in the same order | Leave reverse off | F1, B1, F2, B2 and so on |
| Backs scanned last page first | Turn on Backs are in reverse order | The last back page pairs with the first front |
| One file has more pages | Nothing, it’s handled | The extra pages go at the end |
If the first page of the result is a back side, swap fronts and backs.
PRIVACY
Yes. Interleave PDFs runs in your browser, so the file never leaves your device.
StackPDF opens the PDF in your browser tab and does the work there.
Close the tab and it’s gone. Free results download to your device. Premium can also keep them in My files.
pdf-lib, PDF.js and qpdf do the work, inside your browser.
FAQ
Add the PDF of fronts, then the PDF of backs, and download. Pages are woven together as front 1, back 1, front 2, back 2.
Yes. The free plan includes 1 PDF export a day, with no account. Premium removes the daily limit for $5.99 a month or $39.99 a year.
No. Both files are combined in your browser, so neither one leaves your device.
Turn on Backs are in reverse order before you interleave. The last back page then pairs with the first front.
That’s fine. Pages are paired while both files have them, and the extra pages of the longer file go at the end.
Merge PDF puts whole files one after another. Interleave takes a page from each file in turn, which is what double-sided scans need.