1. A document processing method executable by a microprocessor for generating a binder document by binding a plurality of original documents, the method comprising: a document selection step of selecting, based on a user first selection, the plurality of original documents to be bound; a binder type selection step of selecting, based on a user second selection, a desired binder type of the binder document from among a plurality of binder types stored in advance in a storage unit, wherein each of the stored binder types is set with binder attribute information, which includes type information indicating document types of a document to be bound in the binder document and ordering information indicating an order of the document types indicated by the type information in the binder document, a first acquisition step of acquiring, from the storage unit, the binder attribute information set to the selected binder type; a second acquisition step of acquiring the document types corresponding to the selected plurality of original documents; and a generation step of generating the binder document by extracting the selected original documents having the document type indicated by the type information of the acquired binder attribute information and binding the extracted original documents in the order of document types in the binder document indicated by the ordering information of the acquired binder attribute information.