A printer (100) for printing based on a print job signal sent from a data processing device (200) registers print job signal sending sources and a message corresponding to each sending source in memory (111, 112). A controller (113) detects whether the sending source of a received print job signal is registered in memory. If the sending source is registered, a messaging unit (110, 111) outputs a corresponding message. Sending sources that are permitted to print can also be registered in memory (111, 112). In this case, the controller (113) detects whether the sending source of a received print job signal is registered in memory, and instructs the printer (110) to print only when the sending source is registered as permitted to print.