What Crop PDF does
Crop PDF trims a margin from the top, bottom, left and right of every page. You enter the amounts in points (72 points = 1 inch = 25.4 mm) and the tool sets each page's crop box accordingly. The visible page shrinks; the underlying content is untouched. Use it to cut white borders off scans, remove the printer's marks from a proof, tighten a slide deck for a tablet screen, or trim a wide document so it fills a phone display when zoomed. The work is done in your browser.
How PDF cropping works
A PDF page has several boxes. The media box is the full page as created; the crop box is the region viewers display and printers print. Cropping sets the crop box inside the media box — nothing outside it is deleted, just hidden. That makes the operation lossless and reversible in a full PDF editor, and it is why the file size does not drop: the hidden content is still there. If you need the cropped-away content actually removed (for redaction or file size), rasterize the result with Compress PDF or use a redaction tool.
New crop box = (left, bottom, width − left − right, height − top − bottom)
A4 page 595 × 842 pt, crop 36 pt (½ inch) each side:
visible area = 523 × 770 pt (184 × 272 mm)Points to millimetres and inches
| Points | Inches | Millimetres | Typical use |
|---|---|---|---|
| 18 | 0.25 | 6.4 | Trim a thin scanner border |
| 36 | 0.5 | 12.7 | Remove standard document margins |
| 54 | 0.75 | 19 | |
| 72 | 1.0 | 25.4 | Cut a full inch — deep margins on old scans |
| 28 | 0.39 | 10 | 10 mm |
| 57 | 0.79 | 20 | 20 mm |
Convert from what you measure: millimetres × 2.835 = points; inches × 72 = points.
Finding the right values
- Open the PDF in a viewer that shows the cursor position in points or millimetres (Acrobat, many desktop viewers) and measure the margin.
- Or estimate from the page: A4 documents usually have 20–25 mm margins (57–71 pt); US Letter often 1 inch (72 pt).
- Crop conservatively first — say 30 pt — check the result, then increase. Over-cropping cuts into content; under-cropping is harmless.
- The same values apply to every page. For a document with different margins on left and right pages (bound books), crop the smaller of the two so nothing is lost.
Common uses
- Scans with black or grey borders from the scanner lid — cropping removes them and saves toner when reprinting.
- Reading on tablets and e-readers — cutting wide margins makes text larger at the same zoom.
- Printer marks and bleed — trimming crop marks and colour bars from a print-ready proof for a clean review copy.
- Two-page scans — crop the left half, save, crop the right half, save, then merge to split a book spread into pages.
- Headers and footers — hide a confidential header or a watermark strip along an edge (note that the content remains in the file).