PDF Crop

This tool trims the unwanted blank edges from every page of a PDF by letting you set four margins (top, bottom, left and right), then downloads the cropped copy. Margins are measured in points, where one point is about 1/72 of an inch. It helps to understand how it works. The tool changes the page's CropBox property, which tells viewers to show only the central part of the page. It does not delete anything inside the cropped-away area. In its default mode that makes it suitable for removing excess white margin and unsuitable for hiding sensitive information; if you really need the cropped content gone from the file, tick 'Remove cropped content for real (flatten to images)' (see below). It also has no visual drag-to-crop preview, and every page gets the same margins.

How to use it

1. Click the dashed box that says Click to select a PDF file and choose the PDF to crop.
2. Fill in the four boxes with the distance to remove from each side: Top margin, Bottom margin, Left margin and Right margin. All four start at 20, in points.
3. Optionally tick 'Remove cropped content for real (flatten to images)'. It is off by default, which still just sets the CropBox. When ticked, a red warning appears: every page is rendered to an image (about 2× resolution, JPEG) and a new PDF is built from them, so text becomes non-selectable and unsearchable, links, bookmarks and forms are lost, and the file usually gets much larger.
4. Click Crop & Download. The button reads Processing… while it works (with the flatten option it reads Processing… page N/total, which is slower on big files) and is disabled until a file is chosen.
5. Your browser downloads cropped-result.pdf. Open it and check that no body text was cut off. If you cropped too much or too little, change the numbers and run the original file again.

Units and sizes

One point is 1/72 inch, about 0.353 mm. A portrait A4 page is commonly 595 by 842 points. The following is the actual result of running the same PDF library (pdf-lib). For a 595 by 842 point page with 20 in all four boxes, the crop box starts at (20, 20) and is 555 wide and 802 high. That is the area left after removing 20 from each side. The page's MediaBox stays at 595 by 842, unchanged. To convert a margin to millimetres, multiply points by 0.353; 20 points is about 7 mm.

Limits and known quirks

• All pages share one set of margins. You cannot set margins per page or crop only some pages.
• There is no preview. You estimate the margins from the document and check the result after downloading.
• In the default mode the cropped-away area is still in the file and is simply not shown. Other software may be able to restore the crop box, so do not use it to hide or remove sensitive content, and the file size does not shrink. To really remove it, tick 'Remove cropped content for real (flatten to images)': the cropped area is no longer stored, but the whole file becomes one JPEG image per page (about 2× resolution), text cannot be selected or searched, links, bookmarks, forms and attachments are lost, the file usually grows, and for very large pages the render scale is lowered automatically.
• If the margins add up to the page width (or height) or more, the page shows: The combined crop margins exceed the page size. Please use smaller values and try again. No file is downloaded. Any other failure shows: Processing failed. Please try again.
• An empty box or unreadable input counts as 0, and a negative number is changed to 0.
• For pages with a rotation value, top, bottom, left and right are converted from what you see on screen into the page's real coordinates, and a page origin other than (0, 0) is taken into account.
• Files with an open password and damaged files fail to process.

Why didn't the file get smaller?

In the default mode, because nothing was removed. The tool only changes the crop box, and all text and images on the page are still stored in the file. To genuinely reduce size, use a compression tool or export the document again.

Can I use it to cover up sensitive information?

Not in the default mode. If you tick 'Remove cropped content for real (flatten to images)', the cropped area is not written to the new file, which meets that need, but everything else on the page is still there (as an image), so still open the result and check it. In the default mode, content outside the crop box still exists in the file and a technically capable person can recover it. To remove sensitive content properly, use a true redaction feature, or export a new file that does not contain it.

How do I choose good margin values?

Open the original and estimate how wide the white space around the body is. One centimetre is about 28 points and one inch is exactly 72. Be cautious: start with small values, check the download, then increase gradually so you do not cut off page numbers, headers or text near the edge.

Will it look the same in every viewer?

Most mainstream viewers honour the crop box, but some programs or print settings may ignore it and use the full page. If you will send the result to someone else, open it in the viewer they are likely to use as well.

Privacy and processing

The PDF you choose is read and processed only in your browser by the bundled pdf-lib component, and the page contains no code that uploads it. The processed file is downloaded straight to your device and no copy is kept. Your selections are cleared when you refresh or close the page.