Though not "official documentation" I'd like to mention a relatively recent book (March 2016) on desktop publishing I stumbled across - Designing with LibreOffice
. While essentially on that subject it seems a good general introduction to using styles and templates and so on. The book was written for LibreOffice but the author states it is also applicable to Apache OpenOffice and NeoOffice. http://designingwithlibreoffice.com
It is free to download but a donation would make the author happy and that helps the world go round. If you want a hardcopy book you can purchase that - details at the website.
The author is interviewed here: http://designingwithlibreoffice.com/interview
and gives some good general background information on the development of OpenOffice and its DTP capabilities.
Windows 7 Pro. x64 SP1
Apache OpenOffice 4.1.3
LibreOffice 18.104.22.168 (occasional use)