1. An image processor for combining a computer-readable coded image into a print image of a document including a document data main body and at least one associated data piece, comprising: a controller that generates a print image of a document including an image of at least a part of the associated data and generates a coded image to be combined into the print image, wherein: the controller determines whether or not the generated coded image can be combined into the image portion of the associated data by comparing a size of the generated coded image with a size of an image portion of the associated data, and combines the generated coded image into the image portion of the associated data on the generated print image, if it is determined that combining is possible; if the controller determines that combining is impossible, the controller selects at least enlargement of the image portion of the associated data or deletion of a part of the information included in the coded image, based on the result of comparison between the size of the generated coded image and the size of the image portion of the associated data; and if the controller selects the enlargement of the image portion of the associated data, the controller causes the enlargement processing on the image portion of the associated data, or if the controller selects the deletion of the part of the information included in the coded image, the controller selectively deletes the part of the information included in the coded image and generates an adjusted coded image based on the information after the deletion.