1. An image processing apparatus comprising: a feature value generating unit configured to generate feature values of images of respective pages of a document image including a plurality of pages; an identification number generating unit configured to generate an identification number unique to the document image; and an embedding unit configured to embed the feature values of the images of the respective pages generated by the feature value generating unit, the unique identification number generated by the identification number generating unit, and a total number of pages of the document image in the images of the respective pages.