An apparatus for executing a printing process on the basis of a print job from an external apparatus, comprises a post-processing unit which can apply post-processing for printed paper sheets using paper sheets prepared independently of the printed paper sheets; a detector for detecting in the post-processing means that the paper sheets prepared independently of the printed paper sheets are set; determination means for determining whether or not print start trigger information is attached to the print job, which indicates an instruction to start printing in response to trigger information to start printing; and print control means for, (i) when a print job designated with the post-processing by the post-processing unit is received and it is determined that the print start trigger information is attached to the received print job, delaying a process of the print job until the detector detects that the paper sheets are set, and starting execution of the print job when the detector detects that the paper sheets are set, (ii) and when a print job designated with the post-processing by the post-processing unit is received and it is determined that the print start trigger information is not attached to the received print job, starting the received print job independently of a detection by the detector.