There is described a document data creating apparatus, a document data creating method and a program thereof, which make it possible to improve convenience of both the user and the creator of the document data by effectively utilizing the digital signature. The apparatus for creating document data that include a digital signature, includes: a character recognizing section to recognize a character based on image data inputted; a reliability determining section to determine a reliability degree of the character; a characteristic value calculating section to calculate a characteristic value of the document data; and a digital signature section to attach the characteristic value to the document data. When the reliability determining section determines that the reliability degree of the character is low, the digital signature section attaches a value, which is different from the characteristic value calculated by the characteristic value calculating section, to the document data as the digital signature.