Master PDF Editor is one of two proprietary apps I currently have running on my laptop, and I would definitely say it's worth the price (although once in a while when they update they manage to mess something up, but will usually get around to fixing it eventually).

This was quite a long time ago, but I had a lot of issues with Okular, though I don't remember what exactly (one thing was that if you changed a document's location, Okular would lose all the bookmarks you added to it, but they may have changed it since then, IDK). Evince's commenting features seem a bit rudimentary to me, but I've only used the one from the Mint repo, so there may be a newer version that's better.

There's also PDF4QT which is open source, but is kind of new and may be a bit rough around the edges, although it does look promising.