I've been using DrawBoard PDF on a Surface Pro for my MBA (lots of readings!). It's not perfect, but it's the smoothest experience I've seen thus far, especiall

I've been using DrawBoard PDF on a Surface Pro for my MBA (lots of readings!). It's not perfect, but it's the smoothest experience I've seen thus far, especially in regards to general zooming and panning. You can also customise your own annotation tools in a shortcut bar - very handy. I wouldn't use it for actual note taking though. The stylus support isn't as good as OneNote (Windows 10 app version), and I haven't had any experience using it with typed notes. I use a separate OneNote notebook for long-form notes in addition to the annotated PDF itself. Another caveat, sometimes the "text select / highlight" tool doesn't work properly because the PDF reflow has been broken somehow (i.e. you end up highlighting half a page of text when you only wanted a single line). In these instances I switch to the freehand highlight tool instead.