One of The Better PDF Readers (but no annotations) in my View is the "Perfect Viewer" with it's PDF plugin :
It's a Comic Viewer (CBR,CBZ , etc..), but also supports PDF and can also load pdf's from a Lan Shares (samba/cifs).
It has a tons for configurable options, for color, rendering, touch zones ,as well as productivity ones like,history, bookmarks, auto border detection (removes the margins from pages), etc.
and it's free.
As for margins / fonts etc, Use basic standards and see what suites you best as it's a subjective thing.
Sans Serif Fonts have better readability on electronic devices.Just print documents with couple of different settings/fonts and see what suits your taste. (I personally like as little margins as possible because the tablet bezel itself is big enough of a margin.)
** I am not affiliated with the Perfect Viewer or it's author In anyway, I just use it on daily basis on all my android devices. For my needs,I find it to be better than any pdf reader currently available. (though not the fastest)