Interesting paper: Maya Embar, Louis M. McHough IV, and William R. Wesselman, “Printer watermark obfuscation,” Proceeding

RIIT ’14: Proceedings of the 3rd annual conference on Research in information technology:

Abstract: Most color laser printers manufactured and sold today add “invisible” information to make it easier to determine when a particular document was printed and exactly which printer was used. Some manufacturers have acknowledged the existence of the tracking information in their documentation while others have not. None of them have explained exactly how it works or the scope of the information that is conveyed. There are no laws or regulations that require printer companies to track printer users this way, and none that prevent them from ceasing this practice or providing customers a means to opt out of being tracked. The tracking information is coded by patterns of yellow dots that the printers add to every page they print. The details of the patterns vary by manufacturer and printer model.