How do I combine odd and even page scans into one PDF?

Load the odd-page file and the even-page file, keep the reverse option on if the second stack was flipped as a block, and interleave. The result alternates the two files a page at a time.

Why are my even pages in reverse order?

Because the paper stack was turned over as a single block after the first pass, so the last sheet went through the feeder first. Reversing the second file during the merge undoes it.

What does the stride setting do?

It takes more than one page per turn from each file. A stride of two produces A1, A2, B1, B2, A3, A4 — useful for documents scanned as spreads or two-up.

What happens if the two PDFs have different page counts?

Interleaving continues until one runs out, then the rest of the longer file is appended. Nothing is discarded, and a warning appears when the difference is more than one page.

Does interleaving re-compress the pages?

No. Pages are copied across as they are, so text stays selectable, images keep their original quality, and the file size is roughly the sum of the two inputs.

Interleave PDF Pages

Turn two scan passes back into one document by alternating their pages, reversing the second stack when it was flipped as a block.

Interleave PDF Pages runs entirely in your browser. Your documents are never uploaded to a server.

Open Organize PDF

About Interleave PDF Pages

Scanning a double-sided document on a single-sided feeder leaves you with two files: the odd pages in order, and the even pages in reverse, because the whole stack was flipped at once rather than sheet by sheet. Interleaving alternates the two back into one correct document. This tool does exactly that, with a switch for the reversal, a stride for documents that pair up two pages at a time, and a choice of which file goes first. If one file has more pages than the other, the extras are appended rather than dropped — losing a page silently is worse than an odd tail — and the preview shows the output order before anything is written.

Features

Alternates two PDFs page by page into one document
Reverse switch for a scan stack flipped as a block
Stride setting for taking two or more pages per turn
Choose which document contributes the first page
Extra pages appended rather than dropped
Preview of the output order before exporting
Warning when the two files differ by more than one page
Files are processed entirely in your browser

How to use the Interleave PDF Pages

Drop the odd-page scan into the first slot
Drop the even-page scan into the second
Leave reverse on if the second stack was scanned back to front
Check the output order, then interleave and download

Example

Input

odd.pdf with pages 1,3,5 and even.pdf scanned in reverse as 6,4,2

Output

A1 · B3 · A2 · B2 · A3 · B1 — a six-page document in the right order

Reversing the second file is what turns two feeder passes back into one document.

Common errors & troubleshooting

Every second page is upside down. — That is a rotation problem, not an ordering one — the sheets went through the feeder head-first on the second pass. Interleave first, then rotate the affected pages.
The even pages came out in the wrong order. — Toggle the reverse switch. Whether the second pass is forwards or backwards depends on how the stack was turned over, and the preview shows immediately which way is right.
One file has several more pages than the other. — That usually means the feeder pulled two sheets at once on one pass. The extra pages are appended so nothing is lost, but it is worth re-scanning the short side before filing the result.

Frequently asked questions

How do I combine odd and even page scans into one PDF?: Load the odd-page file and the even-page file, keep the reverse option on if the second stack was flipped as a block, and interleave. The result alternates the two files a page at a time.
Why are my even pages in reverse order?: Because the paper stack was turned over as a single block after the first pass, so the last sheet went through the feeder first. Reversing the second file during the merge undoes it.
What does the stride setting do?: It takes more than one page per turn from each file. A stride of two produces A1, A2, B1, B2, A3, A4 — useful for documents scanned as spreads or two-up.
What happens if the two PDFs have different page counts?: Interleaving continues until one runs out, then the rest of the longer file is appended. Nothing is discarded, and a warning appears when the difference is more than one page.
Does interleaving re-compress the pages?: No. Pages are copied across as they are, so text stays selectable, images keep their original quality, and the file size is roughly the sum of the two inputs.

Related tools

Merge PDFs — Combine multiple PDFs into one, with reordering.
Organize PDF — Reorder, rotate and delete pages from thumbnails, then export.
Split PDF — Extract pages or ranges (e.g. 1-3,5,7-9) into a new PDF.
Rotate PDF — Rotate all pages or a selection by 90/180/270°.
PDF to Single Long Page — Stack every page onto one continuous sheet you scroll instead of paging.
PDF N-up — Print 2, 4, 9 or 16 pages per sheet, with a booklet option for folding.