Crop PDF
Crop PDF pages and trim their margins by dragging a box, typing margins or cutting away the white space.
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How to use Crop PDF
Key features of Crop PDF
The page is shown with the crop box over it and the area to be cut off darkened. Drag any of the eight handles, drag inside the box to move it, or move it with the arrow keys, 1 pt at a time or 10 with Shift.
Type the top, right, bottom and left margins in points, millimetres or inches, the same on all sides or each on its own. Presets set 20, 40 or 60 pt, and the new page size is shown as you go.
Finds the printed content by looking for anything darker than a pale grey, then crops to it with the padding you set. By default it checks each page on its own and leaves a blank page as it was.
Crop all pages, the page shown, odd pages, even pages or a list such as 1-3, 5. For a scanned book, swap left and right on even pages so the inner margin is trimmed on both sides of each spread.
The tool sets each page's crop box with pdf-lib. Viewers show the smaller page, but the content outside the box is still in the file and can be restored by another tool.
The preview comes from pdf.js and the crop is written by pdf-lib, both running in your browser. Nothing is sent to a server.
About Crop PDF
Crop PDF shows a page of your file and lets you set the area to keep, by dragging a box, by typing the margins, or by letting the tool find the printed content. Margins are measured as the page is displayed, so "left" means the left of the page you see, even when the file stores the page turned or already cropped.
When you save, each chosen page gets a new crop box, which viewers and printers treat as the visible page. Nothing is deleted: the content outside the box stays in the file and the file size hardly changes. That makes a crop easy to undo with another tool, and it also means cropping is no way to hide private information.
When to use Crop PDF
A textbook chapter scanned from a bound book has a wide gutter on the inside of every page. Set a larger left margin than right and tick the option that swaps them on even pages, and both sides of each spread lose the gutter.
Slides exported with a wide white border waste paper as handouts. Trim white space with a few points of padding brings each page in to its content, so a print dialog set to fit the page can enlarge what is left.
One page of a scan has a black strip down its right side. Show that page, drag the right edge of the box in past the strip and set Apply to to Page shown only; the other pages keep their full size.
A footer with an internal file path, or a draft mark near the edge, stays in the file after cropping and can be shown again by any tool that resets the crop box. Redact PDF removes text for good, and Remove Watermark targets text repeated on every page.
Tips and troubleshooting
- Margins are measured from the page as it is shown, including any crop the file already has, so crops stack: 40 pt and then 20 pt leaves 60 pt off each side. Start again from the original file to redo a crop.
- Pages of different sizes get the same margins in points, so 60 pt takes a bigger share of a small page. Trim white space with each page checked separately fits every page to its own content instead.
- The box always leaves at least 36 pt (half an inch) of page. A page too small for the margins you typed is skipped and named in the result message rather than cropped away, and the line under the preview says so when that page is shown.
- Rotated pages are handled: top, right, bottom and left mean the page as it appears in the preview, and the crop box is converted to the way the page is stored.
- Trim white space treats anything lighter than a pale grey as paper. A faint scanner shadow or a page number near the edge counts as content and keeps the box larger; drag the box in by hand after detecting. A page whose content already reaches its edges is left as it was, and when no page has any white space the tool says "There was no white space to trim" and makes no file.
- A file that needs a password to open stops with "Could not open this PDF: it needs a password", and one that opens without a password but restricts changes stops with "This PDF is encrypted", both as soon as the file is added. Remove the protection with Unlock PDF first.
- The output is named cropped_ plus your file name, and the message says how many pages were cropped and which, if any, were skipped.
How Crop PDF works in your browser
pdf.js renders the page you are looking at onto a canvas and the crop box is drawn over it. The margins are kept in points, as the page is displayed, so switching pages or resizing the window does not change them. Trim white space renders the page again at one and a half times its size on a white background, finds the outermost pixels darker than a pale grey, and turns that box back into margins with your padding.
pdf-lib opens the original bytes when the file is added, so an encrypted file is refused before you set up the crop. When you click Crop & Download PDF, two opposite corners of each chosen page's visible rectangle are converted to PDF coordinates through that page's own pdf.js viewport, which accounts for a page box that does not start at zero, an earlier crop and a stored rotation, and the result is written as the page's crop box. The document is saved to a Blob behind the Download button; nothing is uploaded.
Frequently asked questions
Can I crop by dragging on the page?
Yes. The page is shown with a crop box over it; drag its edges or corners, or drag inside it to move it. The margins update as you drag, and the dark area is what will be cut off.
Is the cropped-off content really gone?
No. Cropping sets the page's crop box, which tells viewers what to show. The hidden area is still in the file, so do not use it to hide private information.
Can it remove the white margins automatically?
Yes. Trim white space finds the printed content and crops to it with the padding you choose. With Detect the content on each page separately ticked, as it is by default, each page is fitted to its own content and blank pages are left as they were; untick it to use the margins found on the page shown for every chosen page.
Can I crop only one side or only some pages?
Yes. Untick Same on all sides to set each margin on its own, and use Apply to for the page shown, odd pages, even pages or custom pages such as 1-3, 5.
Does cropping make the file smaller?
No. The content outside the crop box is still stored, so the file size stays about the same; only the displayed area shrinks. To reduce file size, use Compress PDF.
How do I undo the crop later?
Nothing was deleted, so any tool that resets or removes the crop box shows the full page again. Cropping the result again cannot undo it, because new margins are measured inside the current crop.
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