Crop PDF pages

What does cropping a PDF actually change?

Cropping changes the page boxes that define which part of a page is shown and printed; it does not redraw the page. This tool sets the MediaBox, CropBox and TrimBox of each chosen page to the new area with the pdf-lib library. These boxes are defined in the PDF specification, ISO 32000-2, and every viewer and printer respects them.

Because all three boxes are set together, the cropped size is the real page size everywhere, not only a view setting in one app. If the source page also has a BleedBox or ArtBox, those are updated to match. Text stays selectable, links keep working, and the page keeps its rotation.

What is cropping a PDF good for?

Cropping is good for removing wide margins, scanner edges and everything around the one part of a page you need. Academic papers and ebooks often have margins that waste space on a tablet or e-reader; trimming them makes the text noticeably larger. Scans usually include the dark edge of the scanner lid or part of the table.

Sometimes only a piece of a page matters: one figure, a receipt from a page of several, or the label area of a shipping document, sized exactly for a label printer. The panel next to the preview shows the page size and the size after cropping in millimetres. An A4 page measures 210 × 297 mm, and US Letter is 216 × 279 mm.

How do you set the crop box?

You set the crop box by dragging, drawing, typing millimetres, using the keyboard or pressing Auto-trim, and all five methods edit the same box. Use whichever fits the job. Dragging is quickest on a phone, typed values are best for print work, and Auto-trim suits scans whose margins differ from page to page.

• Drag the corner or edge handles, or drag inside the box to move it. The handles are large enough to use with a finger.
• Press and drag on the shaded area to draw a new box from scratch.
• Type the trim for each edge in millimetres when you need exact measurements for print.
• With the box focused, arrow keys move it and Shift plus arrow keys resize it.
• Auto-trim detects content on the page, which is ideal for scans with uneven margins.

How is the crop applied to rotated or mixed-size pages?

The box is stored as a proportion of the page you see, then converted into PDF coordinates for each page separately. PDF coordinates are measured in points, where one point is 1/72 inch and one millimetre is about 2.83 points. The conversion accounts for pages that are stored rotated and for pages that already had a crop area, so the result matches the preview.

In All pages mode the same proportions are applied to every page, so documents with mixed page sizes are cropped by the same share of each page. Use Page by page when layouts differ. A crop box smaller than one point in either direction is rejected with a message, because such a page would be unusable.

Auto-trim every page checks each page on your device one at a time, marks the pages where it found margins to remove and switches to Page by page, so you can step through and adjust any page it got wrong. A Stop button ends the scan early on long documents. The preview itself is rendered by pdf.js in your browser.

Does cropping remove the hidden content or shrink the file?

No, cropping hides content instead of deleting it, and the file size stays almost the same. Text and images outside the box remain embedded in the page and can be brought back with PDF editing software. Never rely on cropping to hide confidential details; Redact PDF removes them for good.

For smaller files, run the cropped document through Compress PDF, which reduces the images that are still embedded. Cropping also cannot enlarge a page beyond its original size. The download is named with “cropped” and the original stays untouched on your device, so keep it in case the full pages are needed again.

How do you crop a PDF on a phone, a Mac or a Windows PC?

On every device you open this page in the browser, choose the PDF, adjust the box and press Crop. On iPhone, iPad and Android the handles are sized for fingers, and the page fits a 375-pixel-wide screen. Safari saves the result to the Downloads folder in the Files app; Chrome on Android saves it to Downloads.

On a Mac or Windows PC, a mouse gives finer control, and the arrow keys nudge the box in small steps. Files up to 200 MB are accepted. Password-protected PDFs open after you enter the password. If Auto-trim finds nothing on a scanned page, the background is probably grey instead of white; drag the box by hand for those pages.