A document management system including a two dimensional code region detection portion that detects a two dimensional code region included in image data, obtained by scanning a document to be managed; a two dimensional code decoding portion that decodes document management information included in the two dimensional code; a layout analysis portion that analyzes a layout of the document; a low resolution portion that obtains data in which a background image becomes low resolution; a two dimensional code character and background processing portion that changes the content of the document; a two dimensional code character encoding portion that encodes the two dimensional code; a background encoding portion that encodes data of the background image; a document filing portion that generates a document file; and a file management portion that adds document management information, decoded by the two dimensional decoding portion, to the document file formed by the document filing portion.