1. An image processing apparatus connected to a server, the image processing apparatus comprising: a document image reading section configured to read, among documents constituting a book, an image of a document of at least one page of the book; a document image checking section configured to check the read image of the document read by the document image reading section against registered images of documents stored in the server to determine whether or not the registered image matching the read image exists; a document image acquisition section configured to, when the document image checking section determines that the registered image matching the read image exists, acquire the matching registered image; and a document image printing section configured to form an image on a paper sheet using the registered image acquired by the document image acquisition section.