Interleave pages from two PDFs alternately
WhiskFile Alternate PDF Pages is a free online tool to interleave pages from two PDFs alternately. Files are processed entirely in your browser — nothing is uploaded to any server.
Quick Answer
Interleave pages from two PDFs alternately. WhiskFile's Alternate PDF Pages is free, works in your browser, and requires no account. Your files never leave your device — all processing happens locally.
Upload two PDFs
Upload your front-pages PDF (Document A) and back-pages PDF (Document B). Drag & drop or pick from Google Drive, Dropbox, or OneDrive.
Configure interleave settings
Choose A-first or B-first order, set pages-per-step (default 1), and optionally reverse either document's page order for duplex scan reassembly.
Preview and download
Check the live preview sequence, then click Interleave & Download. Your combined PDF is ready instantly — no upload, no waiting.
Max file size: 50 MB (free) · 500 MB (paid). Processing time: ~8s on average. Batch processing: upload multiple files at once.
Alternate PDF Pages runs entirely in your browser — no software to install. Works on any device with a modern browser.
Windows & Mac
Chrome, Firefox, Edge, Safari
iPhone & Android
Safari, Chrome mobile
iPad & Tablets
Full touch support
Unlike server-based tools that upload your documents, WhiskFile processes everything locally in your browser. Your files never leave your device — not even temporarily.
No upload required
Files are processed in your browser — nothing is sent to any server
100% private
No server storage, no data collection, no third-party access
Works offline
Once loaded, works without an internet connection
“I merge dozens of reports weekly. WhiskFile handles it instantly — no software to install, no sign-up hassle.”
Sarah Chen
Project Manager
“Splitting contracts by section used to take ages. Now I drag, drop, and it's done in seconds.”
David Kim
Legal Assistant
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Client-side processing
This tool now runs entirely in your browser — files never leave your device.
Result preview & sharing
Preview your processed file before downloading, and share results via a secure link.
Interleaving combines two PDFs by alternating pages: page 1 from file A, page 1 from file B, page 2 from file A, and so on. It's the standard way to reassemble double-sided scans.
Yes. When one PDF runs out of pages, the remaining pages from the longer PDF are appended at the end.
Step size controls how many consecutive pages are taken from each document before switching. Default is 1 (true alternation). Setting Doc A to 2 and Doc B to 1 means: take 2 pages from A, then 1 from B, then 2 from A, etc.
When scanning double-sided documents with a flatbed or auto-feed scanner, back pages are often in reverse order. Reversing Document B puts them back in the correct sequence.
No. All processing happens entirely in your browser using pdf-lib. Your PDFs are never uploaded to any server — unlike Sejda or DeftPDF, which require server uploads. Your documents stay completely private.
Upload the front pages as Document A and the back pages as Document B. Enable 'Reverse' on Document B to flip the page order, then interleave. This is the standard fix for auto-feed duplex scanners.
Completely free, with no limits. No page count cap (Sejda limits to 50 pages), no file size cap (DeftPDF limits to 50 MB), and no tasks-per-hour restriction. Use it as much as you need.
No. WhiskFile copies pages directly from the original PDFs without re-compressing or altering content. Quality is fully preserved.
Merge combines files end-to-end (all of File A, then all of File B). Interleave alternates pages between files, which is essential for reassembling double-sided scans or mixing documents page-by-page.
Open whiskfile.com/tools/alternate-pdf in any mobile browser (Safari, Chrome, Firefox). The interface is fully responsive — upload two PDFs, configure settings, and download the interleaved result directly on your phone.
WhiskFile processes files 100% in your browser with no upload, no limits, and a live preview of the output sequence. Sejda uploads files to servers and limits free use to 50 pages / 3 tasks per hour. PDFsam requires a desktop app installation.
Yes. WhiskFile auto-detects encrypted PDFs and processes them using pdf-lib's ignoreEncryption mode.
Yes. WhiskFile is a free browser-based alternative to Adobe Acrobat for interleaving and alternating PDF pages. No software, no subscription, no Adobe account needed.
Yes. Alternate PDF Pages runs entirely in your browser using WebAssembly. Your files are never uploaded to any server — they stay on your device throughout the entire process. No data is transmitted, stored, or accessible to WhiskFile or any third party.
Alternate PDF Pages accepts PDF files as input and produces PDF output. The maximum file size is 50 MB on the free plan (500 MB for Pro users). There are no page count limits.
See how WhiskFile compares to other PDF tools on features, pricing, and privacy.
Chromebook & Linux
Any modern browser
