Crop PDF

Cropping a PDF does not remove content from the file. It changes the page's CropBox, which is the rectangle the viewer uses to decide how much of the page to display. The original artwork outside that rectangle is still in the document, just hidden. This is part of the PDF 1.7 specification (ISO 32000-1) and is why a cropped PDF often has the same file size as the original.

If you need the trimmed area genuinely deleted (for example, to redact a sensitive footer), cropping is the wrong tool. You would need a redaction workflow that flattens and rasterises the visible region. For ordinary tidying, like removing the wide white border on a scan of a book page, cropping is fine and reversible by anyone who reopens the file in a desktop PDF editor.

The most common reason to crop is a bad scan: a phone-camera capture of a contract that includes the table top, or a flatbed scan with a 20mm white border on every page. Removing 10% from each side usually pulls a phone-scan back to just the document. For book pages, an asymmetric crop works better, since the inner gutter margin is usually narrower than the outer.

Crop dimensions are stored in PDF points, where 1 point equals 1/72 of an inch. A standard A4 page is 595 by 842 points, US Letter is 612 by 792. The tool above accepts either points or millimetres, and lets you apply the same crop to every page or just the ones you select.

The crop tool uses pdf-lib loaded directly into your browser. Your file is never uploaded anywhere. That matters for legal documents, NHS letters, payslips, or anything else you would not want sitting in a third-party server's logs. If you have a 200-page scanned bundle, mobile browser memory will be the bottleneck, not network speed; on a phone, files above roughly 50MB may stall.

If your document still has form fields after cropping and you want to lock them in place, use [Flatten PDF](/flatten-pdf) afterwards. To remove pages entirely instead of trimming margins, [Delete PDF Pages](/delete-pdf-pages) is the right tool.