@IrisKalmia I was thinking about adding this advice, but decided not to for clarity. Solid black block are the only way to censor something reliably, but they have to be applied correctly. Countles PDFs, PPTX presentations and vector images were censored with black boxes that can be removed. And that's not all; contract between EU and AstraZeneca although censored correctly had first 255 characters off all paragraphs in table of contents. OPSEC is hard.
@IrisKalmia Also sharpies are not ideal, sometimes little image manipulation can reveal what was underneath. GOOD OPSEC IS HARD
@gorol it is! Ultimately it's about raising how much effort an attacker would need to put it past their effort to give
@gorol Now you have me wondering what ink would be best. I bet lettering over the barcodes and such in a bic would be fairly reliable, but have no study materials