It seems that XPP documentation is only available as individual PDFs that can be downloaded one by one
as a single zip file containing all the PDFs.
However that single zip archive contains only the PDF documents that were available "on the original release date".
At the current time that single zip archive contains the PDF documents from June 2017.
However there are 10 manuals that appear to have been updated since then.
It would be nice to have another single zip of all the latest manuals i.e. a zip that is updated whenever a manual is updated. (or maybe a zip for each point release?)