A method for managing genuine characteristics of both an electronic document and a print medium comprising: a step for recognizing image data contained in the electronic document; a step for applying an extraction condition of an image feature previously determined and must be considered to the recognized image data to calculate a coordinate set corresponding to a pixel or a set of pixels, constituting the image feature; a step for recognizing at least a coordinate value among coordinate values and pixel color values, corresponding to each of coordinates constituting the coordinate set, and for embedding the recognized coordinate value as a code of a digital watermark into the pixel or the pixel set, constituting the image feature, or into an area in the vicinity; and a step for outputting the electronic document where the digital watermark embedding process operation has been carried out to the print medium.