A data processing apparatus makes adding, deleting, and changing of modification rules easy. The data processing apparatus includes an output destination type determining unit that determines type of output destination determined by an output destination determining unit using categorizing information, modification processing units that execute modifying processes different from each other on content of image data, a Plug-in Factory that determines the modifying process by referring to the determined type and content of modifying process set for each categorized type and generates modification processing units that execute the determined modifying processes, and a print commanding unit that requests modification processing units to execute the modifying process, generates output data from the modified image data, and sends the output data to the determined output destination. The content of the categorizing information and modifying process can be customized, and modification processing units can be added or deleted.