Scanned documents often come with wide margins, stray borders, or scanner artifacts around the edges of every page. Cropping removes that dead space so the content fills the page properly — useful before printing, before combining a PDF with other documents that have different page sizes, or simply to make a document easier to read on a phone screen.
Unlike desktop PDF editors that require an install, this tool runs the crop operation directly in your browser using the open-source pdf-lib library. Your file is read into memory, the crop box of every page is adjusted mathematically, and the result is written back out — at no point does the file touch a server. That also means there's no upload wait time, even for large documents.
A quick tip: if you're preparing a document for print, crop conservatively (5-10%) since aggressive cropping can cut off page numbers or footnotes that sit close to the edge. Preview the result before printing multiple copies.