Keep the test file unchanged
Save the exact PDF that will be published and calculate or record a stable file identity if your workflow supports it. Test results should point to that file, not an earlier export with the same name. Record the checker, ruleset, and PDF validator versions so later results can be compared honestly.
Run structural and metadata checks
A PDF checker can inspect whether text is present, a tag tree exists, the default language and title are set, headings and lists have suitable tags, figures have alternative text entries, links have annotations, tables use table structure, and form controls expose required properties. It can also find orphaned content and several forms of invalid structure.
Some results are signals rather than conclusions. A checker may detect that alternative text exists but cannot know whether the wording carries the image's purpose. It may identify a table structure without knowing whether a complicated header association is understandable in the reading tool.
Inspect the tag tree and content order
Compare the structure tree with the visible page. Confirm that headings, paragraphs, lists, tables, figures, captions, and notes appear in a sensible hierarchy. Check that every meaningful object belongs to the tree and that decorative content is marked as an artifact.
Read the content in sequence. Multi-column layouts often reveal jumps that a static page view hides. Footnotes and sidebars need a deliberate position in the reading order. Headings should support navigation instead of merely matching visual typography.
Use the links, tables, and forms
Move through interactive elements with the keyboard. Link text should identify its destination or purpose. Form controls need usable names, instructions, required-state communication, and error recovery. In a table, move cell by cell and confirm that row or column headers provide the expected context.
Review images and visual presentation
Read each alternative in context. Compare it with the image and surrounding text. A decorative image should not interrupt the reading sequence. A complex chart may need a longer explanation or data table beyond the short alternative.
Check text and meaningful graphic contrast, color-dependent instructions, text size, zoom, and reflow behavior where the document supports it. These visual checks sit outside many PDF syntax validators.
Report coverage with the result
A PDF testing result should identify failed checks, passed technical checks, partial signals, required human review, and anything that did not run. Keep object locations and repair notes with the result. After repair, test the new file and attach the retest instead of replacing the earlier evidence.