Official Ubuntu documentation (Server and Desktop) is published on help.ubuntu.com. Anyone can help and there are many ways to do so. See the below link to get started.
https://wiki.ubuntu.com/DocumentationTeam/SystemDocumentation
Peter Matulis
Helping with Ubuntu documentation
Archived thread 2237856 from Documentation and Community Wiki Discussions. Markdown source: Documentation_and_Community_Wiki_Discussions/thread_2237856_Helping_with_Ubuntu_documentation.md