To provide a printer and a printing system for suppressing special sheets of paper from being unreasonably lost.

An MFP 100 determines whether a degradation criterion for admitting a lowered image quality is satisfied or not (S102, S103). If the degradation criterion is met (S103:YES), it determines, based on the attribute of a print job, whether a restriction condition for restricting printing is satisfied or not (S104, S105). As for restriction conditions, for example, a sheet of paper subject to restriction is set in advance, and if the setting of this sheet of paper subject to restriction for use are set on a print job, the restriction condition is satisfied. Further, if the restriction condition is satisfied (S105:YES), printing is restricted.