how to modify the navfooter

Where is the content of the navfooter established?
I would like to make some modifications to this footer, but I am unable to
figure out where the source that generates it.

I am building the documentation following the instructions from "Building
The Documentation" in Appendix J, currently on 9.6.

I am using the command:
make STYLE=website html

I can see the generated navfooter div section in the output html. I must be
missing something, because I cannot find a file in the git branch that
includes the class named "navfooter" or or any other words like "Navigation
footer", "Next", or "Prev".

I have limited understanding of stylesheets (whether dsl or xsl), but I am
hoping that I can make the small modifications needed for our use.

I am also curious about the docFooter div section that appears in the
publicly published PostgreSQL documentation pages. It does not appear when
I build the docs.
Is there a reason that the copyright does not appear on each page when I do
the doc build?
Is there some way to get it included when I do the doc build?
What file is used that contains the format (style?) info for that generated
html div section?

I would appreciate any assistance from those in the community that
understand something about these footers.
...Rick Swagerman