I’d recommend using a dedicated PDF reader in any case.

One advantage of Firefox's PDF reader is that it is sandboxed which a dedicated PDF reader typically isn't AFAIK.

	▲	jimjimjim 6 hours ago \| parent [-]
		Generally speaking most dedicated PDF readers haven't implemented the nastier parts of the PDF spec that need a sandbox. Except adobe. They support everything because they wrote it. But they keep making it worse so I can't recommend them.

I use SumatraPDF for reading, but it doesn't do editing. The Firefox PDF editor works perfectly fine.