Crop PDF

Cropping a PDF works very differently from cropping a JPEG image. When you crop a JPEG, the cropped pixels are permanently deleted. When you crop a PDF, the content outside the crop area is not deleted—it is simply hidden from view.

Every PDF page defines its physical dimensions using five mathematical bounding boxes:

• MediaBox: The physical medium (e.g., A4 paper size).
• CropBox: The visible region that PDF viewers are instructed to display or print. (This is what this tool modifies!)
• BleedBox: Used in professional printing to define the extra area needed to accommodate physical cutting.
• TrimBox: The final intended dimensions of the printed page after cutting.
• ArtBox: Defines the extent of the meaningful content (excluding margins).

Because cropping only adjusts the CropBox (the viewing window), you must never use cropping to hide sensitive information.

If you crop out a paragraph containing a password or a social security number, anyone can open the PDF in a hex editor or specific software, expand the CropBox back to the MediaBox size, and read the "hidden" text. To securely remove sensitive text, you must use a true Redaction tool which physically deletes the object streams from the file.