PDF documentation in Stata 18 

You have many options for accessing Stata 18's over 18,000 pages of
documentation. Explore all the ways you can find the information you
need, whether you want to start from the Help menu and go straight to
the PDFs or start from a command's help file. It also shows you how to
effectively navigate within the PDFs to quickly get to the examples.
For more about the latest PDF documentation in Stata, see
www.stata.com/...