Printed documents have been used as accessories to fraud, terrorist attacks, forgery, and extortion. Tracking down the printer that was used to produce such documents may be beneficial to law enforcement and military agents. Printer identification requires the extraction of a set of features or signatures that uniquely represent the printer. These signatures can be inherent or intrinsic to the printing process, or they can be artificially produced and embedded during the printing process. In this paper, the hidden information for an electrophotographic (EP) printer is generated by altering the laser beam intensity from scan line to scan line, which results in dot gain, and shift in the horizontal position of the dots. Techniques from digital communications are applied to this embedding signal to make it imperceptible, but reliably transmitted and recovered. The embedding signal is inserted in the frames or borders of security documents such as bank notes, statements, and event tickets. Such an embedding scheme offers a content-independent domain for marking the print compared to using text characters or halftone images.