Check the next page that comes out of your color laser printer. It just may have a small pattern of yellow dots that can be used to trace the document back to you.
These dots are used to encode the serial number of each printer into any page printed. Documents can then be traced back to the printer in case of counterfeiting or other illegitimate uses. According to Xeros, who uses this technology in their color laser printers, a code is printed every inch on a printed page. The size and color of the dots make them almost impossible to see with the naked eye. The only way to know is to shine a blue LED light on the page and use a magnifier. Canon is also rumored to use this technology.
According to the US Secret Service the codes are only used in cases of criminal acts.