20. The print processing method according to claim 17 , wherein the second identification information is generated in printing the document image of the electronic document.
17. A print processing method comprising: acquiring first identification information associated with an electronic document; identifying the electronic document by using the first identification information before printing of a document image of the electronic document onto a medium is ended; generating second identification information uniquely specifying the electronic document or the medium at a time of printing the document image of the electronic document and a code image which contains the second identification information onto the medium, wherein the second identification information includes information indicating a printout time at which the document image of the electronic document is printed onto the medium; identifying the electronic document or the medium by using the second identification information after the document image of the electronic document and the code image are printed onto the medium; and associating the first identification information and the second identification information and outputting the first identification information and the second identification information, which are associated with each other to a document management unit, where the document management unit discards information of the first identification information after the document management unit determines, based on the first identification information, a correspondence between the second identification information and the electronic document.