1. An image processing apparatus comprising: a composite image generator that generates a composite image by superimposing, on a document image of a document represented by document data, two-dimensional code images individually corresponding to a plurality of document elements included in the document; and a print controller that causes a printer to print the composite image, wherein the composite image generator determines positions of the two-dimensional code images corresponding to the document elements so that the positions do not overlap images of the document elements, wherein the document elements are sequenced, wherein information represented by each two-dimensional code image is stored in a memory, and wherein the image processing apparatus further comprises an associating unit that associates, with the information represented by each two-dimensional code image corresponding to a corresponding one of the document elements, the information represented by the two-dimensional code images corresponding to the document elements before and after the corresponding one of the document elements.