I want to thank Amanda H, since this is an issue I have been struggling with in my research. I often download PDFs of articles and then need to annotate them, but the default annotation font is often too large and certainly does not need a snazzy outline around it. The people I share these notes with are smart. They don't need flashing lights in their eyes to understand that they should read something and get back to me.
Her explanation and GIFs showed me how to use Evernote much better.
If Evernote were to add a great feature for me, it would be to do these annotations in a sidebar outside of the margins of each PDF or article, so I could add them as footnotes or comments rather than trying to squeeze them into the margins.