Crop PDF
Choose a PDF
The file is read in this page and never uploaded.
Cropping trims the margins of PDF pages by setting a crop box. The rectangle a viewer displays. It is the right tool for reclaiming the enormous white margins on a scanned book page or an academic paper being read on a tablet. It is the wrong tool for hiding anything, and the page says why.
How it works
A PDF page carries several boxes. The media box is the physical sheet; the crop box is the region a viewer actually displays. Setting a smaller crop box changes what is shown without altering the content underneath it.
- Margins are given in points, the PDF unit: 72 points to the inch, so 72 trims one inch and about 28 trims a centimetre.
- The coordinate origin is the bottom-left corner, so the top margin is subtracted from the height rather than added to the origin, handled for you, but it explains why the numbers behave as they do.
- A4 is 595 × 842 points and Letter is 612 × 792, which is the usual starting point for working out sensible margins.
- The range control accepts 1-3, 7, 12- and so on, so a document with different margins on odd and even pages can be handled in two passes.
The content outside the crop box is still in the file. Any viewer or tool can reset the box and reveal it, which makes cropping useless as redaction. If material must not be seen, remove it from the source document before producing the PDF.
Examples
Trimming an inch all round
Margins
72 points on each side
Result
A4 becomes 451 × 698 points
595 - 144 and 842 - 144. The visible area shrinks; the page content is unchanged.
A scanned book page
Margins
Large left margin, small right
Result
The gutter removed, text centred
Scanned books have an oversized inner margin from the binding. Cropping it makes the page far more readable on a tablet.
Margins that are too large
Margins
400 top and bottom on A4
Result
Refused: nothing would remain
800 points of margin exceeds the 842-point height, so the page would have no visible area at all.
Frequently asked questions
Does cropping delete the content outside the box?
No. It sets the region a viewer displays, and everything outside it remains in the file. Resetting the crop box brings it straight back. Never use cropping to hide sensitive content, remove it from the source document instead.
What is a point?
The PDF unit of length: 72 points to the inch. So 72 points trims one inch, about 28 points trims a centimetre, and 36 points trims half an inch. A4 is 595 × 842 points and US Letter is 612 × 792.
Why is the file the same size after cropping?
Because nothing was removed. The content streams, fonts and images are all still there; only the crop box values changed. A crop that genuinely reduced file size would have to re-render every page, which would lose text selectability.
Can I crop different amounts on different pages?
Yes, by running it more than once with different page ranges. A scanned book usually needs one setting for odd pages and the mirror image for even ones, since the binding gutter alternates sides, two passes handles that.
Will the crop survive printing?
Usually. Most printers honour the crop box and scale the visible region to the sheet, which is why a cropped page prints larger. Some print pipelines use the media box instead and print the whole original page. Check a single page before committing to a long print run.