The present image processing apparatus externally receives document data, obtains attribute information that indicates information on matters from a matter management server, and transmits the received document data and the obtained attribute information on individual matter data to a document management server. The document management server presents, in accordance with a request from an external apparatus, the transmitted document data and attribute information on matters to the external apparatus, and receives, from the external apparatus, association information that is selected in accordance with the presented information and associates the document data with the matter data, and registers, together with the association information, the corresponding document data in the matter management server.