You applied redaction. The viewer shows clean black bars in the editing view. Distribute the file, and recipients say they don't see the bars — or see them inconsistently.
What's actually going wrong
Annotation-layer redaction. The bars are in an annotation layer that some viewers don't render. Wrong opacity. Bars set to low opacity invisible against the page. Render bug. Specific viewer fails to draw redaction marks.
The quick fix
Use Flint's redact PDF which applies redaction as flattened page content, not annotations. Bars appear in every viewer because they're part of the page itself.
After redacting, verify in multiple viewers — browser, mobile, desktop. Consistent visibility everywhere means the redaction is properly applied.
If that didn't work
If bars appear in some viewers but not others, the redaction wasn't flattened. Open in Flint's editor and use 'save as flat PDF' to bake the redaction into the page.
For PDFs already distributed with invisible-in-some-viewers redaction, the redaction may have technically removed content (verify by selection) but presentation is inconsistent. Republish with flattened version.
Prevent it next time
Use redaction tools that flatten by default. Verify in multiple viewers before distributing. And treat redacted distribution as a multi-step process: redact, flatten, verify, then ship.
FAQ
Why are my redaction bars invisible in some viewers?
Annotation layer not rendered. Flatten the bars into the page (Flint's redact tool does this by default).
Is invisible redaction still effective?
If the underlying content was actually removed (not just visually covered), yes — the data is gone regardless of visible bars. But inconsistent visibility looks unprofessional and creates uncertainty.
How do I verify redaction worked?
Try selecting text in the redacted area in multiple viewers. If selection consistently produces nothing, content is genuinely removed.
Can I add visible marks to existing real redaction?
Yes — open the redacted PDF and add black rectangles where the redaction occurred. Flatten. Now visible bars complement actual content removal.
Visible and real redaction every time. Use Flint's redact tool — flatten, verify, ship.