iface->get_n_pages = ps_document_get_n_pages;
iface->set_page = ps_document_set_page;
iface->get_page = ps_document_get_page;
iface->get_n_pages = ps_document_get_n_pages;
iface->set_page = ps_document_set_page;
iface->get_page = ps_document_get_page;