1. An image processing apparatus capable of reading a document that has a ground design and carrying out image processing, the apparatus comprising: a latent image visualizing portion that visualizes a latent image included in the ground design; a first modification processor that carries out a modification process comprising at least intensifying a portion of the latent image so that the latent image included in the ground design is not visualized; an authenticating portion that performs authentication regarding whether or not a user is an authorized user of the document; and a controller that performs control so that the modification process is performed by the first modification processor in order for the latent image included in the ground design not to be visualized, or performs control so that the latent image included in the ground design is not visualized by the latent image visualizing portion, only when the user has been authenticated as an authorized user of the document.