1. A printing apparatus comprising: a printing unit comprising a plurality of print sheets having different sizes, the printing unit being able to carry out printing selectively on any of the print sheets; an original document size determining unit to determine a size of an original document; a scanning unit to scan the original document; a region recognizing unit to recognize a region to be printed in the original document scanned by the scanning unit; a deciding unit to decide a print sheet size being larger than the region to be printed and smaller than the size of the original document by comparing the sizes of the print sheets with the size of the original document determined by the original document size determining unit and a size of the region to be printed recognized by the region recognizing unit; and a controlling unit to cause printing of an image of the recognized region to be printed at 100% magnification on one of the print sheets having the size decided by the deciding unit.