1. A non-transitory computer-readable medium storing computer-executable instructions that, when executed by a processor, cause an output apparatus, which includes a storage section configured to store a plurality of document data sets having a predetermined order and acquired from a plurality of documents, the plurality of document data sets each comprising image data and a plurality of attributes, wherein each of the plurality of attributes is associated with one or more sequential images of the image data, the attributes selected from the group consisting of a cover, a table of contents, body text, non-body text, and an afterward, the output apparatus further comprising an output section configured to output, on a display, images of the image data to perform: a first output control process of controlling the output section to sequentially output, on the display, each image of image data belonging to one document data set and, thereafter, sequentially output, on the display, each image of image data belonging to a next document data set, wherein the next document data set is based on the predetermined order; and a second output control process of controlling the output section to sequentially output on the display, each image of the image data belonging to a specified attribute of one document data set and, thereafter, sequentially output, on the display, each image of the image data belonging to the specified attribute of the next document data set, each of the plurality of document data sets having a plurality of attributes including the specified attribute, and wherein the storage section is configured to store each of the plurality of document data sets in sections based on the plurality of attributes.