A black rectangle can look convincing while the original text remains selectable, searchable, or extractable underneath. That is concealment, not reliable redaction.
What permanent redaction must remove
A safe output must not retain the covered text, form value, annotation, vector object, or hidden layer. WatermarkPDF handles selected redaction regions by rendering each affected page locally, replacing those pixels, and rebuilding that page as a new image.
The trade-off
Flattening reliably removes underlying page objects, but affected pages lose searchable text and vector sharpness. Choose a suitable output resolution and inspect the result at high zoom.
Redaction checklist
- Cover the full sensitive field, including labels if they disclose meaning.
- Check repeated headers, footers, and attachments.
- Download and reopen the result.
- Try selecting or searching for the removed text.
- Keep the original in a separate secure location.
Do not rely on appearance alone. Always verify the downloaded document before sharing it.