I use SumatraPDF for reading, but it doesn't do editing. The Firefox PDF editor works perfectly fine.
In latest pre-release it does editing too (annotations, filling out forms, extracting pages, deleting pages etc.)
One advantage of Firefox's PDF reader is that it is sandboxed which a dedicated PDF reader typically isn't AFAIK.
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.
For Linux users, SELinux's sandbox command works well. (The manual isn't event two printed pages.)