Alternate Merge PDF — Interleave Two PDF Files
Combine two PDF files by interleaving their pages alternately. Perfect for merging separately scanned front and back pages of double-sided documents. All processing stays in your browser.
Key Features
Page-by-Page Interleaving
Combine two PDF files by alternating pages — page 1 of file A, page 1 of file B, page 2 of file A, page 2 of file B, and so on. Perfect for merging double-sided scans.
Reverse Second File
Optionally reverse the second PDF's page order. This handles back-to-front scans where the back pages were scanned in reverse order, reconstructing the original document correctly.
Perfect for Double-Sided Scans
Scan front pages of a double-sided document into one file and back pages into another, then interleave them to reconstruct the original page order automatically.
100% Private & Secure
All processing happens locally in your browser using pdf-lib. Your PDF files never leave your device — no uploads to any server, complete privacy.
No Installation Required
No software to download or install. The tool runs entirely in your browser — works on any device with a modern browser.
About This Alternate Merge Tool
Our Alternate Merge tool combines two PDF files by interleaving their pages alternately using pdf-lib. The pages are merged in this order: page 1 of the first PDF, page 1 of the second PDF, page 2 of the first PDF, page 2 of the second PDF, and so on. This is particularly useful for reconstructing double-sided scanned documents. If you scanned the front pages into one PDF and the back pages into another, enable the Reverse Second PDF option when the back pages were scanned in reverse order (last page first). The output preserves all original content and formatting from both source files. If one file has more pages than the other, the remaining pages are appended at the end. All processing stays local in your browser — no data is ever uploaded.
How to Alternate Merge PDFs — Step by Step
Alternate merging two PDFs with our tool is simple:
Upload the First PDF
Upload the first PDF file (for example, the front pages of a double-sided document).
Upload the Second PDF
Upload the second PDF file (for example, the back pages). If the back pages were scanned in reverse order, keep the Reverse Second PDF option enabled.
Configure Options
Toggle the Reverse Second PDF option as needed. This is essential when back pages were scanned from last to first.
Merge and Download
Click Alternate Merge to interleave the pages. Download the merged PDF, or click Clear to start over with different files.
Important Notes
This tool interleaves pages alternately using pdf-lib, preserving all original content and formatting. If one PDF has more pages, the remaining pages are appended at the end. The Reverse Second PDF option is intended for double-sided scans where back pages were scanned in reverse order. Encrypted PDFs cannot be processed — please decrypt them first.