How it works
Two passes over the file
The structural pass reads the PDF's own dictionaries: its version, the media, crop, trim and bleed boxes of every page, whether fonts are embedded, and whether pages use transparency. The content pass then replays each page with pdf.js and records which colour spaces are painted and where raster images land.
Findings are sorted into errors, warnings and notes. Pick a page to see its boxes drawn over a preview and only the findings that belong to it.
Bleed and image resolution
Print shops usually want 3 mm of bleed beyond the trim box. The tool flags pages with no bleed box, with less than 3 mm, or with no trim box at all.
Image resolution is the pixel width of the picture divided by the inches it covers on the page after scaling. Very low values are errors and borderline values are warnings.
effective ppi = image pixels ÷ (placed width in points ÷ 72)
