How to crop the margins off a PDF
- Measure before you cut
The reader reports page dimensions. A typical A4 document has 20 to 25 mm of margin on each side.
- Start conservatively
Try 15 mm and look at the result. It is quicker than undoing an over-aggressive crop.
- Watch the outer edges
Page numbers and running headers live in the margin, and are the first things a crop removes.
- Crop and read it
Check the busiest page, not the first one.
Why this matters for exam and study documents
Reading a past paper on a 10-inch tablet is transformed by a 20 mm crop. The question text roughly doubles in effective size with no zooming at all.
What is kept, what changes, and what this will not do
These change how a document presents itself rather than what it contains - with one important exception, which is that cropping hides content without removing it.
Kept
- All page content - cropping hides, it does not delete
- Text, fonts, images and the searchable text layer
- File size, almost unchanged
Changed
- The visible page boundary and therefore the printed area
- Content outside the new boundary is not displayed, but is still in the file
Limits
- Cropping does not remove content from the file. Anyone can restore the full page with another tool, so never use it to conceal anything.
- The same trim is applied to every selected page, so a document with varying margins needs more than one pass.
Questions and answers
Is cropped content really still in the file?
Yes, and this matters. Cropping changes the page boundary; the objects outside it remain. If something needs to be genuinely gone, use Redact PDF, which deletes it.
Does cropping make the file smaller?
Barely. The content is still there, so there is very little to save.
Can I undo a crop?
Not from the result with the tools here. Keep the original.