MediaBox, CropBox and UserUnit: the limits of a geometry preflight

A PDF rectangle is a coordinate range, not automatically a physical sheet measurement. To interpret it, keep the raw coordinates, effective clipping and scale separate.

Compute a visible rectangle, then scale it

The inspector retains MediaBox and CropBox and uses their intersection for the effective visible area. For two rectangles, the left and bottom edges are the maxima of their corresponding edges; right and top are the minima. A CropBox outside the MediaBox is reported even if the intersection still has a useful area. An empty intersection is not assigned a made-up positive size.

width_pt  = (right - left) × UserUnit
height_pt = (top - bottom) × UserUnit
mm        = pt × 25.4 / 72

At UserUnit 2, a 300-unit width measures 600 points, not 300. After scaling, a quarter-turn rotation of 90 or 270 degrees swaps width and height. Zero or 180 degrees does not. Non-quarter-turn values are flagged rather than presented as a trustworthy normal displayed size.

Use groups as a navigation aid

Dimensions are rounded for reporting and grouping. A group that differs from the most common page size is an inspection cue, not evidence that the page is broken. A document may intentionally include foldouts, inserts or landscape tables. The report does not render page content or inspect every optional PDF page box.

Read metadata cautiously

Title, author and creator fields are statements stored in the file; they may be absent, stale or forged. A missing author is not proof of anonymization, and an author string is not identity verification. The tool does not inspect hidden content for privacy or validate signatures.

An encrypted file that cannot be opened without a password is reported as restricted, without invented page details. The utility does not crack passwords or bypass permissions. Successful parsing is also not a comprehensive PDF conformance test. Keep the original and make editing decisions in a separate workflow.

If the geometry warrants an intentional edit, KomoPDF is the related editing product. Carry the page number and box values into that separate decision; this inspection does not guarantee repair, signature preservation or secure redaction.