Firefox is pretty good these days, but I'm not sure about all of this feature creep. Seems like much of this could just live as extensions.
The one place where I wish they'd invest would be in getting AEC (audio echo cancellation) up to par so I could use Firefox for my WebRTC calls at work.
The PDF features are actually an extension, just one built in as Firefox's default pdf viewer.
It's called pdf.js https://github.com/mozilla/pdf.js/
You can actually use this pdf viewer in another browser like Chrome if you'd like, there's a demo URL on there.
SurfingKeys browser extension does (or used to) bundle this extension