See the demonstration video posted to my YouTube channel:
This example set uses PDFs redacted with three different programs. While this approach may not find any kind of redaction made to a PDF, it will help you find redactions made with widely used techniques, and expedite the review of large document sets.
1. The first PDF contains redactions made with the tool used in Adobe Acrobat.
2. The second PDF has redactions made with the highlighting tool of PDF Viewer Plus.Text was highlighted in black and then the file was written to a new PDF.
3. The last PDF has redactions made in Nuance Power PDF.
4. Use the Preflight tool in the Print Production menu.If this menu is not visible look for it in the drop down menu underneath where it says 'Comment'.
5. On the Profiles tab in the PDF analysis section, select:'List page objects, grouped by type of object'. . . then click 'Analyze' at the bottom right
6. On the Results tab, look for 'Vector objects (filled)' in the tree.
7. You should see indications that there are black objects on particular pages. Click the 'Show' button on the right to be taken directly to the redaction.
8. In the second sample PDF, the redaction will not be found with the page object analysis.
9. It's on page 3 but no object is found on that page.
10. To find this redaction, go to the Options menu on the right and select:Browse Internal PDF Structure
11. In the windows that opens, we can find an annotation listed under the specific page number at Parent\Kids\Annots
12. We can search in the Find box on the top for a reference to:/S:Highlight. . . or perhaps:/S:Redact. . . and we'll find the exact page on which the redaction appears.
13. In the third example PDF, the redactions made with the Nuance Power PDF tool can be found using the page object analysis, as with the sample with Acrobat redactions.