Comic PDF Preflight

What a printer looks at first

Before anyone looks at your art, a preflight script checks the geometry of the PDF. This tool runs the same checks in your browser, reading page boxes with pdf.js and pdf-lib. It never uploads the file.

• Page count. Interior files should be a multiple of four. You choose the padding; a printer will pad at the back.
• Consistency. Every page the same size and orientation, including pages turned by a rotation setting. One rotated page stops a whole job.
• Size against your spec. Pages should equal trim plus bleed. Trim-size pages mean no bleed. Pages two trims wide look like unsplit spreads. Checking a cover, a single front cover at trim plus bleed passes, and so does a wraparound: trim height plus bleed tall and at least two trims plus the outside bleed wide. The extra width is reported as the spine.
• TrimBox. A PDF with bleed needs a TrimBox on every page so the printer knows where to cut. The tool names any page without one and compares the rest with your trim size; on a wraparound cover only the height is compared.
• CropBox. A CropBox smaller than the page is noted: PDF viewers show only the CropBox, so bleed can look missing on screen.
• Image resolution and fonts. Where pdf.js exposes them, embedded images are checked at their placed size, and every font the pages use is checked for embedding.

Tolerances

Sizes within 0.02 in (about 1.4 points) are treated as equal, which absorbs the rounding that PDF exporters introduce. Anything further off is reported. Files over 500 pages are checked on the first 500; the page count covers them all. Read how to prepare a comic PDF for printing for export settings that pass first time.

Questions