Example use
You have a stack of double-sided paperwork, but your scanner only supports one-sided scans. Scan the fronts, flip the stack, scan the backs, then merge both PDFs here.
Build a duplex PDF from two simplex scan passes
Use this when your scanner cannot scan both sides automatically. Scan the front sides into one PDF, scan the back sides into a second PDF, then merge them into one correctly ordered document.
Free Duplex PDF Builder
Upload a front-side PDF and a back-side PDF, then combine them into one finished file.
Before & after
This should be the PDF from the first pass, such as pages 1, 3, 5, and 7 scanned front-side only.
This should be the PDF from the second pass, such as pages 2, 4, 6, and 8 scanned after flipping the stack.
Tip: Most second-pass back-side scans need the back pages reversed before interleaving. If the pages come out upside down, turn on the rotation option.