A document processing apparatus that acquires a definition file associated with a document file that stores information that serves as a key for acquiring fragments. The definition file specifies a rule used for acquiring the fragments from other document files based upon the key stored in the document file. The document processing apparatus reads out sub-document files based upon the key specified in the document file and the rule specified in the definition file. The document processing apparatus arranges these fragments thus acquired so as to build a virtual document, and presents the virtual document thus built to the user.