Crop a PDF
Trim the margins and see exactly what you are keeping before you commit. Or let it find where the content stops on its own — the usual answer for a scan. Nothing is uploaded.
Why crop at all
Three reasons come up again and again. A scan carries a border the scanner added rather than anything on the document. A photographed page has a desk round the edges. And a document built for A4 is being read on a phone, where the margins waste a third of a screen that is already small.
Cropping fixes all three without touching the content, which is why it is worth doing before anything else: the page looks the way it should, and every later step works on what you actually want to keep.
Detect content, and when not to trust it
The detector renders the first page and finds the rectangle where non-white pixels stop, then leaves a small margin around it. On a typical scan that lands within a millimetre or two of the right answer.
It measures the first page only, because measuring every page and taking the union would give you the widest margin in the document rather than a tight crop. If page one is unrepresentative — a cover sheet, or a page with a footer the others do not have — check the number it produces before applying it to the whole file.
What it does to the file
| Property | Effect |
|---|---|
| Text and links | Untouched — still selectable and clickable |
| Image quality | Unchanged; nothing is re-encoded |
| File size | Roughly the same. Cropping hides margins, it does not delete them |
| Page dimensions | Reduced to the crop, so readers and printers use the new size |
Common questions
Does cropping make the file smaller?
Usually only slightly. Cropping sets the page boundary rather than deleting anything, so the content outside it is hidden but still in the file. If you need a specific size, crop first and then run the result through the compressor.
Is it reversible?
In principle yes, because nothing is removed - the crop is a box in the page record. A later tool can widen it again. That also means a crop is not a way to hide sensitive material: the content is still there.
What does "Detect content" do?
It renders the first page and finds the box where the ink actually stops, then pads it slightly. On a scan with a grey border, or a photo of a document on a desk, that is usually the crop you wanted.
Will text still be selectable?
Yes. Cropping does not re-encode the page, so text, links and image quality are exactly as they were.
Can I crop only some pages?
Yes. Leave the page box as "all", or give a range such as 1-3, 7. Margins are percentages, so they apply sensibly to mixed page sizes.
What about sideways pages?
Margins follow the page as you see it, not the file’s internal orientation. A page stored rotated is handled so that "top" means the top of what you are looking at.