This is a breakthrough. It has been rumoured for years that printers and copy machines include secret codes on documents to track them back to the source machine but the EFF now has real evidence and even tools that you can use to perhaps decode your printer's secret tracking information.
This guide is part of the Machine Identification Code Technology project. It explains how to read the date, time, and printer serial number from forensic tracking codes in a Xerox DocuColor color laser printout. This information is the result of research by Robert Lee, Seth Schoen, Patrick Murphy, Joel Alwen, and Andrew "bunnie" Huang. We acknowledge the assistance of EFF supporters who have contributed sample printouts to give us material to study. We are still looking for help in this research; we are asking the public to submit test sheets or join the printers mailing list to participate in our reverse engineering efforts.