An offline installer is also available and can be found on the downloads page, https://smartflows.xpertdoc.com/downloads. The offline installers are distributed as zipfiles. To install, you should unpack the zipfile to a local folder. Next, double click on the file xpertdoc-template-builder.vsto to install the Template Builder add-in into Word. Make sure to keep the unpacked files in place, when Word is started, it will read the files from there.
Also, this installer will only install for the active user, you can't do a machine install with this installer.