1. An image processing device comprising: an image acquiring unit configured to acquire image data from one or more document sheets set thereon; an image extracting unit configured to extract, from the acquired image data, respective document images based on the document sheets; an image position specifying unit configured to specify a position of each of the extracted document images which position is defined on the acquired image data; a first identification provider configured to provide each of the document images with a first identification for identifying the document image, based on the specified positions of the document images; an input unit configured to input ancillary data each piece of which is for creating an ancillary image; a second identification provider configured to provide each piece of the input ancillary data with a second identification for identifying the piece of the ancillary data; an ancillary data identifying unit configured to identify a piece of the ancillary data as being associated with each of the document images, based on the first and second identifications; a set data generator configured to generate set data each piece of which has a set of a document image and an ancillary image based on ancillary data identified by the ancillary image identifying unit as being associated with the document image; a determining unit configured to determine whether a total number of the ancillary images based on the input data is equal to a total number of the document images extracted; an adjuster configured to, when the determining unit determines that the total number of the ancillary images is different from the total number of the document images, make an adjustment such that the total number of the ancillary images is equal to the total number of the document images; a data generation controller configured to take control of the set data generator to generate the set data based on the document images and the ancillary images after the adjustment by the adjuster; and an output unit configured to output the set data generated by the set data generator under the control by the data generation controller.