Crop a PDF: trim the margins in millimetres

How it works

1. Measure what you want gone. Print one page, put a ruler on it, and read off how much white you want off each side. Millimetres, because that is what rulers and printer trays are marked in.
2. Enter the four trims. Top, bottom, left and right, each independently, and at least one of them above zero. The sides are named as you see them on screen, so a page stored sideways still trims the edge you are pointing at.
3. Look at the result before you commit. Open it and check the pages with the most content — a table that runs wide, a footnote at the foot. If a trim was a millimetre too keen, crop the original again rather than cropping the crop.

What the options do

The form above lists the options this tool is running today, straight from the server. This is what they are for.

Pages to crop

Which pages the four trims apply to. Leave it at ‘all’ for a document scanned in one pass on one machine. Name pages when the scan is uneven — a book photographed page by page usually has a wide gutter on the left of the right-hand pages and on the right of the left-hand ones, so you run it twice, once with ‘odd’ and once with ‘even’, with the left and right figures swapped. You can write 1-5, 3,7,9, or 4- for everything from page four on.

Trim from the top (mm)

The head of the page. This is where a scanner’s black bar lands when the sheet was smaller than the platen, and where a running header sits that you would rather not carry into a bundle. Be careful of anything you plan to add later: headers and page numbers are placed relative to the cropped edge, so crop first and stamp afterwards, or the stamp will sit in space you have not yet trimmed.

Trim from the bottom (mm)

The foot. Usually the old page number, a print date, or a shadow where the sheet lifted off the glass. If you are producing a bundle that will be numbered afterwards, trimming the original number away here and adding your own is much cleaner than leaving two numbers on the page — and again, do the cropping first.

Trim from the left (mm)

The binding side of a right-hand page: the gutter shadow from a book scan, and the ragged half-circles left by a three-hole punch. Take less than you think at first. A left trim that eats into the first character of each line is the most common way to make a document that reads fine on screen and prints unusably.

Trim from the right (mm)

The outer edge of a right-hand page, and the place a sheet-fed scanner most often leaves a grey stripe where the paper ended and the backing began. All four sides are named as they appear on screen rather than as they are stored, so a page carrying a quarter turn has its trims rotated for you — you point at the edge you can see and that is the edge that goes.

What this tool does not do

• Cropping is not redaction. The margin is hidden, not deleted: whatever was in it is still in the file, and anyone can widen the crop box back out in under a minute. If a name or a number has to be gone for good, it has to be removed from the content, and no crop of any kind will do that.
• It takes straight millimetres off each side and nothing else. There is no lasso, no rotation of the crop, and no automatic detection of where the white space ends — you give it numbers.
• The same four numbers apply to every page you name. Where the gutter alternates sides, run it twice, once for ‘odd’ and once for ‘even’.
• It will refuse trims that would leave a page under about 2 mm across, and it tells you that page’s real size in millimetres so you can try again with sensible figures.
• The file does not get meaningfully smaller. The content in the margins is still there, unrendered — compress is the tool that actually reduces the size.
• A few programs ignore the crop box and print the full sheet regardless. Modern readers and printers honour it, but if a colleague reports the margins are back, that is why.

What happens to your file

The file is uploaded because Crop PDF runs on our server rather than in the browser tab. It is kept for at most 2 hours and the result you download for 24 hours, then a scheduled job deletes both — a job has to be able to read the file while it runs, and you have to be able to retry a failed conversion without re-uploading. Neither needs longer.

Nothing about the contents is logged, and no one reads your documents. The retention page lists the same numbers the code enforces, and the privacy policy says who can reach the storage they sit in.

Questions

Can someone get the cropped margin back?

Yes, easily, and you should assume they will. The content is untouched; only the window onto it has moved. Any tool that can set a crop box — including this one — can set it back to the full sheet. Treat cropping as presentation, never as removal.

Does cropping make the PDF smaller?

Hardly at all. Everything that was in the margins is still stored in the file, just not displayed. If size is the problem, run compress; if the margins were part of a scanned image, the image is one object and cropping the page does not cut it up.

How do I know how many millimetres to take off?

Print a representative page at 100% and measure it with a ruler. Failing that, most readers show the pointer position in millimetres somewhere in the status bar. Start conservatively — you can always crop the original again with bigger numbers, whereas an over-crop means starting over.

My book scan has the gutter on a different side on each page.

Run it twice. Once with ‘odd’ and the shadow figure in the left box, once with ‘even’ and the same figure in the right box. Feed the result of the first run into the second.

It refused my trim values.

The numbers you gave would have left a page barely a couple of millimetres across, which no reader displays usefully. The message includes that page’s actual width and height in millimetres, which is usually enough to spot the typo — a 210 mm page cannot lose 200 mm from the left.

Will page numbers I add afterwards land in the right place?

Yes. The page numbers, header and footer and Bates tools all measure their margin from the cropped edge, so a number set 12 mm from the bottom sits 12 mm above the new foot of the page. Crop first, stamp second.