How to merge duplex scans into one PDF

1 min read·25 July 2026

Scanner without automatic document feeder? Then you scan the front sides and back sides separately. With PDFrust's duplex tool you merge them in the correct order — page 1 front, page 1 back, page 2 front, etc.

The problem with flatbed scanners

With a flatbed scanner you scan page by page manually. For double-sided documents you scan all fronts first (1, 2, 3…) then all backs (…3, 2, 1 — reversed, because you flip the document). The backs must then be interleaved in reverse order.

Duplex tool in PDFrust

Open the duplex scan merge tool on PDFrust. Upload the front pages as the first PDF and the back pages as the second. Check "Back pages reversed" if you flipped the document (default). PDFrust automatically combines the pages in the correct order: 1f, 1b, 2f, 2b…

Merge duplex scan

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Check the result

Download the combined PDF and open it to verify the order is correct. Is a page upside down or out of order? Use the organise tool to reorder or rotate pages.

Tips for better scans

Scan at 300 dpi for readable documents. For archiving choose 600 dpi; then compress via PDFrust. Keep fronts and backs in separate folders to avoid confusion.