Printing apparatus

A printing apparatus capable of performing differential printing to print differences between a print-target image data set to be printed and a reference-source image data set to be compared during differential printing, comprising:

• a storage unit that stores image data sets;
• a printing unit that performs printing based on the image data sets;
• a differential print request accepting unit that accepts differential print requests;
• a differential extraction unit that, if the differential print request accepting unit accepts a differential print request, compares the print-target image data set with the reference-source image data set, and extracts a difference between them;
• a differential thumbnail image creating unit that places a mark on an area containing the difference, which is extracted by the differential extraction unit, in a page of the print-target image data set, and creates a differential thumbnail image which is a thumbnail image of the page containing the difference;
• and
• an output control unit that performs control operations to output the differential thumbnail image created by the differential thumbnail image creating unit.