To provide a technique capable of inexpensively discriminating the manager of a distributed document who generates an illegally copied document or the like when the document or the like is collected.

Seal data are prepared, mask data composed of a pixel set in which each pixel value is decided with a random number are prepared as many as the number of copies which corresponds to document distribution destinations, enciphered seal data in which the exclusive OR operation value of pixel values corresponding on each pixel position is defined as a pixel value are calculated about the mask data and the seal data, each piece of enciphered seal data and document data prepared in each piece of the mask data are respectively united to prepare a distribution document, and the distribution destinations of the distribution document are associated with the mask data used to prepare the enciphered seal data united with the distribution document and recorded as a distribution destination management data table. In the case of confirming the distribution destinations, each piece of mask data is printed on a transparent or translucent medium as mask data for collation, the enciphered seal data part of the distribution document is overlapped on the mask data for collation, and when the seal data are displayed at the enciphered seal data part, a distribution destination is specified.