@njp,
I have a question, I’m sure it’s easily answered.
In which case you might expect there will probably already be a post about it…
Is there some code that I need to have on any specific page (or the site as a whole) so it can re-download the CSS every time somebody visits/refreshes a page? (or a setting even).
This a technique that is often referred to as cache-busting. See this earlier post on this forum: Cache-busting and assets. Especially reply #8