A document processing technique which provides an editing function of, e.g., combining separately created document files into one document file is disclosed. When an instruction to insert the second document file to the first document file displayed in the display region is input, candidates for the insertion method of the second document file in inserting the second document file to the first document file are presented in accordance with the input instruction. The second document file is inserted to the first document file on the basis of the insertion method selected from the presented candidates.