Displaying of document information to be printed in a printing apparatus capable of inserting, during printing on print sheets fed from a predetermined sheet feed unit, a plurality of types of sheets from sheet feed units different from the predetermined sheet feed unit, is controlled by setting information on an insert sheet to be inserted in document information, determining for each page of the document information and of the set insert sheet whether or not the page is printable or unprintable, and controlling to differently display a printable page and an unprintable page in accordance with the determination result.