A printing system includes a host terminal apparatus (e.g., personal computer) and an image forming apparatus (e.g., printer). The personal computer transmits print data to the printer. The printer is connected to the host terminal apparatus over a network, the printer being capable of embedding a watermark pattern into the print data received from the host terminal apparatus. The watermark pattern contains an item of information that identifies a user who actually picks up a printed output of said image forming apparatus. The watermark pattern contains information that identifies a user who activates printing of the print data. The printer includes a user identifying section that identifies a user who actually picks up the printed output.