1. A printing system including a printer for which particular information is set as a qualification designation and a host device for transmitting print information created by a particular application to the printer, wherein: the particular application has an information adding unit for appending added information corresponding to the particular information to the print information; and the printer comprises a decision unit for deciding whether the print information transmitted from the host device includes the added information and the added information corresponds to the particular information, and a print processing unit that executes printing of the print information if the decision unit decides that the print information includes the added information and that the added information corresponds to the particular information, discards the print information if the decision unit decides that the print information does not include the added information, and discards the print information if the decision unit decides that the print information includes the added information but the added information does not correspond to the particular information.