1. An image scanning device, comprising: a conveying component configured to convey a document sheet placed on a document placing platen to a plurality of locations; a scanning component configured to scan paper fingerprint information on the document sheet; a comparing component configured to compare a first set of paper fingerprint information, which is scanned by the scanning component while holding the document sheet in place at a first location, with a second set of paper fingerprint information, which is scanned by the scanning component while holding the document sheet in place at a second location; and an acquiring component configured to acquire the paper fingerprint information if the comparing component detects that the first set of paper fingerprint information is coincident with the second set of paper fingerprint information.