Can you add highlighter of the text into Firefox PDF reader. For me this is more important than adding text and drawing in it.
Christmas is coming, so we won't make it in time for 122.
You can test the feature, even if it is not complete yet, in Firefox Nightly by setting pdfjs.enableHighlightEditor to true in about:config.
Highlighting is now enabled by default in Nightly, no need to tweak config anymore.
We are thinking to release the feature in 123 at this point, only few things are missing (you can follow along on https://bugzilla.mozilla.org/show_bug.cgi?id=1846098).