Update README.md to include information about the new pipeline

README.md

@@ -18,9 +18,20 @@ If the repository was cloned in a standard way, it is possible to checkout submo
 
 `git submodule update --init `
 
-## Building the documentation
+## Building the doumentation
 
-To generate the PDF version of manual(s) use the following:
+### Automatic build
+
+A pipeline is setup to run automatically whenever a push occurs on a branch. On average it takes about 6 minutes to run. The automatically generated PDF will be titled with the branch name instead of a version number to reflect its development status. The branch name is passed using the $CI_COMMIT_REF_NAME environment variable created by the runner when it checks out the git branch in the virtual execution environment.
+
+The pipeline method is mainly intended to check the validity of changes made to the LaTeX files but it is useful for infrequent contributors who would otherwise struggle to maintain a suitable LaTeX build environment on their own platforms.
+
+The compiled PDF versions of the manuals are available for a short period (15 minutes) after a successful pipeline completion. At this stage, they are pipeline `artifacts` and there are several ways to access them.
+Probably the easiest is to go directly to the CI/CD pipeline tab (from the left sidebar) where all the pipelines executed will be listed (https://forge.nemo-ocean.eu/nemo/doc/manuals/-/pipelines) . On the right of each successfil pipeline there is a download button to Download the artifacts.
+
+### Manual build
+
+Regular contributors to the reference manuals are likely to maintain LaTex build environments on their local resources [ TODO: add description of LaTeX packages required to build manuals ]. The `manual_build.sh` script can be used to generate the PDF version of manual(s) in a local environment as follows:
 
 ```
 ./manual_build.sh [-c] [-p] [-r version ] manual_name