Comment by TacticalCoder

I then convert the image to grayscale only. Then I apply a filter so that only 16 colors are used. And I then adjust brightness/contrast so that "white is really white". It's all scripted: "screenshot to PDF". One of my oldest shell script.

16 shades of grey (not 50) is plenty enough for text to still be smooth.

I do it for several reasons, one of them being I often take manual notes on official documents (which infuriates my wife btw) but then sometimes I need to then scan the documents and send them (local IRS / notary / bank / whatever). So I'll just scan then I'll fill rectangle with white where I took handnotes. Another reason is when there's paper printed on two sides, at scan times sometimes if the paper is thin / ink is thick, the other side shall show.

I wonder how that'd work vs adversarial inputs: never really thought about it.