PDF Crop — Trim Margins and Resize Pages

PDF documents define their visible area through a system of rectangular boundaries called page boxes. The PDF specification (ISO 32000-2:2020) defines five such boxes, and understanding how they interact explains what cropping actually does and, just as importantly, what it does not do.

The CropBox and how it differs from the MediaBox

Every PDF page has a MediaBox that sets the absolute physical extent of the page — the maximum possible boundary. The CropBox defines the region that PDF viewers display on screen and that printers reproduce on paper. When no CropBox is present, viewers default to the MediaBox. This tool sets the CropBox to a rectangle smaller than the MediaBox, effectively hiding content outside that rectangle without deleting it. An A4 page measures 595 x 842 points, US Letter is 612 x 792 points, and Legal is 612 x 1008 points.

Crucially, modifying the CropBox does not remove content from the file. The underlying page stream retains all original graphics, text, and embedded images. A PDF editor that resets or ignores the CropBox would reveal everything that was hidden. This non-destructive behavior is intentional — it preserves the option of undoing or adjusting the crop later. For permanent content removal, you would need to rasterize the page at the CropBox boundary using Rasterize PDF.

The five PDF page boxes

The PDF specification defines five page boundary rectangles, each serving a distinct purpose. The MediaBox is the only required box and sets the absolute page size. The CropBox clips the visible content area and defaults to the MediaBox when absent. The BleedBox extends 3-5 mm beyond the TrimBox to provide a bleed allowance for commercial printing. The TrimBox defines the intended final cut line — the finished page after trimming. The ArtBox marks the meaningful content area, excluding margins and running headers. This tool operates exclusively on the CropBox, leaving the other four boxes unchanged.

PDF coordinate system and units

PDF dimensions use a coordinate system with the origin at the bottom-left corner of the MediaBox. The X axis increases to the right and the Y axis increases upward — the inverse of the screen coordinate system used by HTML Canvas and most web rendering. All measurements are in points, where one point equals exactly 1/72 of an inch (0.352778 mm). The margin values you enter represent points to trim inward from each edge. For example, setting Left to 72 removes the leftmost inch of the page from the visible area.

Page range syntax

The Custom Range input accepts comma-separated page numbers and hyphenated ranges. For example, 1-5,8,10-12 crops pages 1 through 5, page 8, and pages 10 through 12. Page numbers are 1-based (the first page is page 1). The Odd and Even options use the human-readable numbering: Odd selects pages 1, 3, 5, and so on.

All processing runs in your browser using pdf-lib, a pure JavaScript library for creating and modifying PDF documents. Your file is never uploaded to any server. To reduce file size after cropping, use PDF Compress. To inspect all five page boxes in detail, try PDF Page Dimensions.

Cropping PDFs addresses real needs across academic, professional, and creative workflows:

• Research papers and ebooks — Academic PDFs frequently have oversized margins designed for print binding and annotation. Cropping them produces a tighter layout that is far easier to read on tablets, e-readers, and mobile devices where screen real estate is limited. A 72-point crop on all sides typically reclaims 20-30% of visible area on standard A4 journal pages.
• Scanned documents — Flatbed and feeder scanners often capture more area than the actual page, leaving dark edges, scanner lid artifacts, or inconsistent borders. Uniform cropping removes these artifacts and produces clean, professional-looking pages.
• Presentation slides — Slides exported from PowerPoint, Keynote, or Google Slides sometimes include letter-boxing when the slide aspect ratio does not match the target page size. Cropping removes the black bars and maximizes the content area for on-screen viewing.
• Print prepress preparation — Designers use the CropBox to align visible content with the TrimBox before sending files to commercial printers. This ensures that proof viewers show the finished trim area rather than the full bleed and slug zones, reducing miscommunication with print shops.
• Legal and regulatory filings — Court filings and compliance submissions have strict margin requirements. Cropping standardizes margins across documents merged from different sources, ensuring consistent presentation. After cropping, run the result through PDF Compress to meet electronic filing size limits.
• Booklet and portfolio assembly — When assembling multi-page booklets with PDF Booklet Creator, uniform page cropping ensures clean imposition and consistent margins across every page of the finished saddle-stitched output.

Processing locally in your browser eliminates the privacy concerns of cloud-based PDF tools. Confidential contracts, unpublished manuscripts, medical records, and proprietary design files remain on your device throughout the entire operation. No data is transmitted, stored, or logged by any external server. For additional page manipulation, explore PDF Split to divide documents or PDF Delete Pages to remove unwanted pages entirely.