Scans come with borders: the white frame of the scanner bed, the shadow at the binding edge, margins sized for a printer you do not own. Oversized margins make text small on screen and waste paper in print. This tool trims them — you set how much comes off each edge, in millimetres or as a percentage of each page, and every page's visible area is tightened to match, on your device.
What cropping a PDF actually does
A PDF page has boxes inside boxes: the content is drawn on a large canvas (the media box), and viewers display a window into it (the crop box). Cropping moves that window. This tool sets each page's crop box with pdf-lib (an open-source library running locally in your browser), inset from the box the page is currently viewed through — so cropping an already-cropped file trims from what you see, not from some hidden original. Two honest consequences. Hidden is not deleted: the content outside the window still exists in the file, so the file size barely changes, and the crop can be reversed later in a desktop editor by widening the box again. Never crop as a way to remove sensitive content — use it for framing, not redaction. And display follows the box: readers, browsers and printers all honour the crop box, so the trimmed page is how the document will genuinely look everywhere.
Millimetres or percent?
Millimetres are the physical language of paper: “take 10 mm off every edge” means the same thing on A4 and Letter, and is the right unit when you are matching a printer's unprintable border or trimming a known scanner frame. Percent is proportional: 5% trims more from a poster page than from a paperback page, which suits mixed-size documents — reports with landscape chart pages, say — where the same physical trim would bite unevenly. The preview shades exactly what will be trimmed on page 1, and the stats panel reports the visible area that will remain, in points (1 pt = 1/72 inch), so there are no surprises at the save step. If the trims would leave a page under 10 points in either direction, the tool refuses rather than produce a sliver.
All pages, or just the first
Uniform documents — a scanned book, a report from one source — want the same trim everywhere, and “All pages” applies your margins to each page relative to its own size. “First page only” exists for the common exception: a cover or title page framed differently from the body, or a test run before committing a 300-page file. Crop the first page, check it in your reader, then return and crop all pages with the same numbers — your original is never modified, so the two-step route costs nothing.
Private by design
Like every CalcViso file tool, this one runs entirely in your browser. The file you choose is read by this page, processed on your device, and offered back as a download — it is never uploaded to a server, never stored, and never seen by anyone else. Close the tab and it is gone from memory.
Worked example
Press the sample button: a 2-page sample (A4, 595 × 842 pt) loads with 10 mm trims preset — the preview shades a border all round, and the stats promise a visible area of about 538 × 785 pt. Press Crop PDF and open cropped.pdf in any reader: both pages display at the trimmed size, the sample's coloured blocks sitting closer to the edges, the generous white frame gone.
How to use this tool
- Drop your PDF onto the box (or create the sample); page 1 previews with the current trims shaded.
- Choose the unit: millimetres for physical trims, percent for proportional ones.
- Set the four trims — each edge is independent, so asymmetric crops (more off the binding side) are fine.
- Check the shaded preview and the “Visible area after crop” figure in the stats.
- Choose All pages or First page only, press Crop PDF, and open the result to confirm the framing.
Crop or scale? Two different fixes
Cropping is often confused with resizing. Crop (this tool) changes which part of the page is visible and therefore the page's displayed shape; the content keeps its original size, which is why text looks bigger afterwards — the same words in a smaller window. Scaling changes the content itself, shrinking or enlarging everything on the page while the window stays put. If a page “has too much margin”, you want crop. If a document designed for A3 must print on A4, your printer's “fit to page” already scales at print time and no file edit is needed at all. And if a scan's margins hide an image-heavy file that is also too large to email, crop for framing, then Compress PDF for size — in that order.