What permanent redaction actually means
Permanent redaction means the words are removed from the file, not covered up inside it. Drawing a black rectangle over text in a PDF adds a drawing on top and leaves the text exactly where it was, so anybody can select it, copy it, or pull it out with a script. Olbo removes the text itself, which is why what it hands back cannot be recovered.
How the failure happens
A PDF holds its text as text and its drawings as drawings, in separate instructions. A black rectangle is an instruction to paint a black rectangle. It does not delete anything, and the reader draws it after the words, so the words are underneath rather than gone.
This has gone wrong in public repeatedly, in filed court documents, in released government papers and in company reports. In every case the file looked right on screen and gave up its contents to anybody who selected the page and pressed copy.
How to check a file yourself
Open the redacted copy, select the area where the covered text was, copy it, and paste it somewhere you can read. If the words come back, the file was not redacted, it was decorated.
The other check is to search the document for a word you know was covered. A reader's own find will happily match text that is underneath a rectangle.
What Olbo does instead
The covered text is taken out of the document when the copy is written, so a paste or a search has nothing to return. The status line says so while you work, and it says it in those words rather than in a claim about security.
On a page with no text on it, a scan, there is nothing to remove and the boxes you draw are burnt into the picture instead. Same outcome, different mechanism, and the tool tells you which one it is doing.
More guides
Olbo is an office suite that runs in your browser. Your files are read on the machine you are sitting at and are never uploaded. See all six tools.