1. An image processing device configured to change a size of original image data representing an original image so as to create size-changed image data representing a size-changed image and output the size-changed image data to an output device in order to show an image within an image formation area in an output image, the image processing device comprising: an image size determination unit configured to determine a target image size of the size-changed image data that is to be created, based on a ratio of a predetermined standard character size to a character size regarding character data included in the original image data and based on an image size of the original image data; an image data creating unit configured to change the size of the original image data so as to create the size-changed image data, based on the determined target image size; and an output control unit configured to control an output of the created size-changed image data to the output device such that the size-changed image is shown within the image formation area in the output image.