The RMR User's Guide is managed as source in the RMR repo from which PDF, Markdown, RST, and plain ASCII text versions may be generated.
The User's guide is automatically published to the read the docs site and linked to the main page:
https://docs.o-ran-sc.org/projects/o-ran-sc-ric-plt-lib-rmr/en/latest/index.html
The original guide for historical purposes is attached (circa August 2019)