They already add hidden tracking dots to documents: https://en.wikipedia.org/wiki/Machine_Identification_Code https://en.wikipedia.org/wiki/Machine_Identificati

They already add hidden tracking dots to documents: https://en.wikipedia.org/wiki/Machine_Identification_Code https://en.wikipedia.org/wiki/Machine_Identification_Code I don't know how this is legal without informing the user. But that's the case with a lot of censorship/surveillance technology - they not only want to keep surveil/censor, they want to do so while keeping users in the dark about it.