Printing system, printing apparatus, document replacement apparatus, and printer driver

A printing data generating unit designates a first section (page numbers, etc.) corresponding to a change target part of a before-being-changed document and a second section corresponding to printing data of a changed part. A printing unit includes a replacement processing portion. The replacement processing portion determines whether or not the section of the counted number of sheets of paper matches the first section, and when they match, instructs the printing unit to print the printing data of the changed part corresponding to the second section, and when they do not match, causes the before-being-changed document to be discharged directly from the printing unit, and thereby replacing just the first section of the before-being-changed document with a document of the changed part corresponding to the second section.