Comment by bryanrasmussen

Or if the document is just text, simply scan it in black and white (as in, binary, not grayscale).

Perhaps an imagemagick pipeline dumping each page out as a png then blanking areas associated with a list of words (a pixel level concordance of the coordinates of all the words having been compiled from a text dump? Hand-waving here).

I'm probably overthinking this one but the various lengths of the redaction bars would provide some information perhaps? So three conspirators with names like Stonk, Hephalump and Pragma-Sasquatch would be sort of easy to distinguish between if the public had a limited list of people who might be involved?