How to use it
- Choose the PDF. Its page count appears under the name, and the first page appears as a preview.
- Type the Top margin, Right margin, Bottom margin and Left margin in millimetres. A margin of 10 mm takes 10 mm off that edge of each chosen page.
- Leave Pages empty for every page, or type pages such as 1-3, 8. Tick Also change the paper size to set the paper itself to the new area, not only what viewers show.
- Optional: drag a box over the preview to keep only that area; the margins are set from it. Then click Crop pages and Download.
What a crop changes
A PDF page has a crop box, the area that viewers and printers show, and a media box, the paper it is printed on. Cropping sets the crop box inside the margins you choose. With the paper option ticked, the media box is set to the same area as well.
Nothing is deleted. The content outside the new box stays in the file, hidden. If something hidden must be gone for good, for example a name under a black bar, use a redaction tool instead.
Millimetres, and pages that are turned
Margins are measured on the page as you see it. A 10 mm top margin cuts the top of the page even when the page is turned by a quarter, so the sides you set are always the sides you see. One millimetre is about 2.83 points, the unit PDF uses, and 25.4 millimetres make an inch.
A page always keeps at least 10 mm in each direction. When the margins would leave less, the file is not cropped at all, and the message names the first page that is too small.
- Pages that are not in the Pages list keep their size.
- The crop works on the visible area of each page, so a page cropped twice keeps the first crop as its starting point.
Example: a scanned A4 letter with a wide white border
An A4 page is 210 by 297 mm. Its scan has about 15 mm of white paper on every side. Type 15 in all four margin boxes, leave Pages empty and tick the paper size option.
Every page becomes 180 by 267 mm, with the text in the middle and no white border, ready for printing or for a smaller file.
Frequently asked questions
Are my PDF files uploaded anywhere?
No. Your browser reads the file, draws the preview and makes the cropped copy on your own device. Nothing is sent to our server.
Does cropping remove the text outside the box?
No. The content outside the new box stays in the file and is only hidden. If you need that content removed for good, use a redaction tool before you share the file.
Why does the tool refuse my margins?
Each page must keep at least 10 mm in both directions. When your margins would leave less on a page, nothing is changed and the message names that page, so you can use smaller margins or leave the page out.
What does the paper size option do?
It also sets the media box, the paper size a printer uses, to the cropped area. Without it, only the crop box changes, and viewers show the cropped area while printers may still use the full paper.
Can I crop only some pages?
Yes. Type the pages in the Pages box, for example 2-4, 7. The other pages keep their size and content.
Does it work on a phone?
Yes, in any up-to-date browser. Type the margins with the number keys, and drag a box over the preview with your finger to set them.
Sources
- pdf-lib, the open-source library that sets the crop and media boxes in your browser
- pdf-lib documentation: reading and changing existing PDFs, their page boxes, document information and form fields
Figures and text last checked on Tuesday, November 10, 2026.