Crop PDF
Trim page margins with precise numeric control.
Top, bottom, left, right — in millimeters, inches, or points. Files never leave your device.
Set margins
Each margin trims from the visible region of every page.
About PDF cropping
How precision cropping works
Cropping a PDF doesn't delete the trimmed area — it sets a CropBox dict entry on every page that tells viewers to show only the visible region. The original page geometry (the MediaBox) stays intact, so the crop is reversible by any tool that respects MediaBox. pdfmundo's cropper reads each page's existing CropBox (which falls back to MediaBox if no crop has been applied before), subtracts your margins in the unit you chose, and writes the new rectangle back. Everything runs in your browser tab — the PDF never travels to a server.
When numeric crop beats drag-to-crop
Most online PDF croppers ship drag-to-crop only. That's fine for trimming one page by eye, but it breaks down when you need precision: removing exactly 3mm of bleed from a print-ready document, trimming a uniform 12mm from every page of a scanned legal filing, or stripping a 35mm speaker-notes footer from every slide of a deck. Numeric margins are repeatable across files — same input, same result every time. For a one-off visual trim, drag-to-crop is fine; for production workflows, numbers win.
The trade-offs
CropBox-only crop is non-destructive but is ignored by some legacy print paths that read MediaBox directly. For modern PDF viewers (Adobe Reader, browser viewers, Apple Preview) and most printers, CropBox is respected. v1 applies the same margins to every page; per-page distinct margins and visual drag-to-crop ship later. If your scan is rotated, run Rotate PDF first — cropping an upright page is easier to reason about than cropping a sideways one.
How browser-based cropping compares
Server-based croppers (Smallpdf, iLovePDF, the Acrobat web service) upload your PDF, crop it on remote servers, and return a link. For a public marketing PDF that's fine; for an unredacted contract or financial filing, it isn't. pdfmundo crops entirely in your browser — the file doesn't leave your device. After cropping, run Compress PDF if you need a smaller file (cropping shrinks the visible region but the underlying page data still lives in the PDF). If you want just the cropped region as an image, PDF→JPG rasterizes the CropBox.
Common mistakes
Setting margins larger than the page is the most common pitfall — the tool rejects this cleanly with a per-page error, but the fix is checking your unit before submitting (10in margins on a Letter page leaves nothing visible). Second: expecting cropping to reduce file size. CropBox is metadata; the trimmed content still sits in the file. Run a compressor after if size matters. Third: cropping a digitally-signed PDF. Any byte change invalidates the signature, so crop before signing, not after. Fourth: expecting MediaBox to change — by design, it doesn't. The crop is reversible.
Frequently asked questions
- What happens if I crop more than the page width?
- The tool rejects the request and tells you which page failed. Reduce the offending margins and try again. The check runs per-page, so a mixed-size document where some pages are too narrow for the requested margins will surface the first failing page.
- Will my original PDF be modified?
- No. pdfmundo only adds a CropBox dict entry on every page; the underlying MediaBox (the original page geometry) stays intact. Any tool that respects MediaBox can read the original dimensions and effectively undo the crop.
- What's the difference between mm, inches, and points?
- Millimeters are the metric default; inches match Letter/Legal layouts; points (pt) are the PDF spec's native unit (1pt = 1/72 inch). Pick whichever matches the source you measured against. The tool converts to points internally before applying margins.
- Can I crop only some pages, not all of them?
- Not in v1 — margins apply uniformly to every page. Per-page distinct cropping ships in v1.1 alongside the visual drag-to-crop interface.
- What if my PDF is password-protected?
- The tool can't read encrypted PDFs. Remove the password in your PDF software first if you have it, then come back here. Cropping an encrypted PDF surfaces a dedicated error explaining this.
- My printer ignores the crop. Why?
- Some legacy print paths read MediaBox directly and ignore CropBox. Most modern printers respect CropBox; if yours doesn't, a permanent crop (MediaBox mutation) is a v1.1 candidate. For now, you can re-export the cropped PDF through a viewer that supports flattening CropBox into MediaBox.
- Does cropping reduce file size?
- No. CropBox is a metadata dict entry — the trimmed content still lives in the underlying page data. After cropping, run Compress PDF if you want a smaller file.
- What's the maximum file size?
- 50 MB on the free tier — same cap as Rotate PDF, Delete Pages, Extract Pages, Page Numbers, and Watermark. The tool processes files entirely in your browser, so the cap is set by typical browser memory rather than a server quota.
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