I'm unsure if either of these help you with regards to HTML and PDF?

https://orgmode.org/manual/LaTeX_002fPDF-export-commands.htm...

https://orgmode.org/guide/HTML-Export.html

I should add, this is `org-export-dispatch`, bound to C-c C-e by default. You can then press `lp` for PDF or `hh` for HTML.

Also, if you're interested, there are HTML themes here: https://github.com/fniessen/org-html-themes