Compare the export with its intended setup
Use the final PDF you intend to submit, within the 650 MB file limit. Match the trim, binding, paper, ink, and bleed settings to that export. Interior checks support paperback and hardcover; cover checks support paperback only.
For a cover, supply the book's final even page count, not the number of pages in the cover file. The cover PDF itself must contain one page. This check does not silently round an odd book count. Interior checks use the actual page count read from the PDF.
Follow a possible issue to its page or property, then compare the measured and expected values in the report. An unreadable file or unsupported extraction is different from a completed measurement. If you change the file or settings during inspection, the old work is cleared; run the check for the new selection.
The selected PDF is read in your browser, without uploading it. Copy and download actions export a text report, not a repaired PDF or a visual preview.
A measurement is narrower than an approval
The checker reads page count, dimensions, mixed page sizes, and available PDF page boxes. It also reports font-embedding information, measurable image resolution, and file or content warnings where extraction supports them.
Unknown means the check could not establish the fact. Not measured means no usable measurement was made; not declared describes missing explicit metadata. None is a pass. A missing optional page box is not automatically a defect, because PDF boxes can have defaults. The PDF 1.7 reference defines those boxes and their relationships.
The size comparison uses the page's MediaBox and a stack127 tolerance of 0.02 inch. That tolerance is a local comparison rule, not an allowance published by KDP. A report with no measurable issues means only that the implemented checks found none.
Interior bleed and cover bleed are different calculations
For an interior without bleed, expected page size matches the trim. With bleed, the expected page gains 0.125 inch in width and 0.25 inch in height. The extra width is asymmetric because interior bleed is added at the outside edge, not both sides. See KDP's trim, bleed, and margin guidance.
A paperback cover combines back, spine, front, and outer bleed. Its expected spine depends on the final book page count and selected paper and ink, so checking a cover against an earlier manuscript count can produce the wrong expectation. The paperback cover requirements are the source for that geometry.
Some print problems need a visual or manual check
Embedded-font evidence does not prove a commercial font license. Image-resolution checks apply only to placements the parser can measure; they do not prove that every image will print well. The checker cannot verify visible ink bounds, safe margins, gutter placement, color acceptance, or barcode placement, and it does not render a preview for visual review.
Correct the source document, export again, and recheck the final file. Then use KDP's Print Previewer and current formatting and review guidance. The report's dated ruleset does not replace KDP's submission requirements or its review of your upload.