What does alternate merge actually do?

It interleaves pages instead of appending them. With two files you get A1, B1, A2, B2 and so on; with more files the pages cycle through each document in turn — a page from file 1, then file 2, then file 3, then back to file 1.

How do I recombine a duplex scan?

Scan all the front sides into one PDF, flip the stack and scan the backs into a second PDF. Add both files here — fronts first, backs second — and interleave. If the back-side scan came out in reverse order, switch on Reverse for that file first.

What happens if the files have different page counts?

Pages interleave until the shorter files run out, then the leftover pages from the longest file are appended at the end. Nothing is dropped.

Can I interleave more than two PDFs?

Yes. Add as many PDFs as you need — pages cycle through the whole list round-robin. Drag the files into the order the pages should alternate in.

My back-side scan is in reverse order. Do I need to rescan?

No. Each file has a Reverse switch that flips its page order before interleaving, so a back-to-front scan zips together correctly without rescanning.

Can I check the result before downloading?

Yes. The output order preview shows the exact page sequence the interleave will produce, so you can confirm the arrangement before generating the PDF.

Are my PDFs uploaded to a server?

No. Reading, reordering and writing the PDF all happen locally in your browser. Your documents never leave your device.

Does it work on my phone?

Yes. The file list, drag reordering and page-order settings all work in a mobile browser, with the settings reachable in a bottom sheet.

Ghép PDF xen kẽ trang cho bản scan hai mặt

Kết hợp nhiều PDF bằng cách xen kẽ trang — A1, B1, A2, B2 — thay vì nối tiếp. Lý tưởng cho scan hai mặt; miễn phí, riêng tư, chạy trong trình duyệt.

1. Add your PDFs

Drop in two or more PDFs — like a front-side stack and a back-side stack from a single-sided scanner.

2. Arrange and reverse

Drag files into interleave order and flip any document that was scanned back-to-front.

3. Download

Get one PDF with pages zipped together — a page from each file in turn, leftovers at the end.

About Alternate Merge

Zip Pages Together Instead of Stacking Them

A normal merge appends one document after another: all of file A, then all of file B. Alternate merge interleaves them — page 1 from each file, then page 2 from each, and so on — the way a zipper closes. If one file is longer than the others, its leftover pages are appended at the end, so nothing is lost.

The classic use case is duplex scanning on a single-sided scanner. You scan the front of every page into one PDF, flip the stack, scan the backs into a second PDF, and interleave the two to reconstruct the original double-sided document. But it works for any set of PDFs — two files or ten — whenever pages need to alternate rather than concatenate.

What You Can Control

The output order is fully determined by the file order and a per-file reverse switch.

Drag to Reorder

The interleave order follows the file list exactly — drag documents until the sequence matches how the pages should alternate.

Reverse Any Document

Scanned the back sides face-down so they came out last-to-first? Flip that file with one switch and the interleave comes out right.

Two Files or Ten

Interleave isn't limited to pairs — pages cycle through every file in the list, round-robin, until each runs out.

Preview the Output Order

Check the resulting page sequence before you commit, so a misordered scan never makes it into the final PDF.

Built for Duplex Scans — and Everything Like Them

Single-sided scanners are everywhere: flatbeds, phone scanning apps, feeder scanners without a duplex unit. The two-pass workflow they force — fronts first, then backs — leaves you with two PDFs that are useless until they're interleaved. This tool closes that gap in seconds, including the common case where the back-side stack came out reversed.

Beyond scanning, alternate merge handles any round-robin assembly: combining odd and even page exports, weaving chapter files that were split per source, or reconstructing a document that was separated into parallel streams.

How It Compares

Regular merge concatenates. Alternate merge interleaves — a different job entirely.

Tính năng	OxygenPDF	Regular PDF merge	Manual page shuffling
Interleaved page order (A1, B1, A2, B2)
Reverse a back-to-front scan
More than two files at once
Leftover pages appended automatically
Preview output order first
No file upload required

Your Scans Never Leave Your Device

Scanned documents are usually the sensitive kind — contracts, medical records, ID copies, signed forms. Most online PDF tools upload your files to a server to process them, which means copies of those documents sitting on infrastructure you don't control.

OxygenPDF reads, reorders and writes the PDF entirely in your browser. Nothing is transmitted, and closing the tab wipes the data. For documents you'd hesitate to email, client-side processing is the safe default.