Ubuntu: Using pdftk to stitch together two-sided PDF
There are many consumer side printers that provide the ability to scan a document to PDF. But unless you have a high-end series, the printer may only be capable of scanning one side at a time, which means you end up with a “front.pdf” and “back.pdf”. If you have a Linux desktop or laptop, luckily … Ubuntu: Using pdftk to stitch together two-sided PDF