From the DEVONtechnologies blog:

In addition, we’ve made PDF annotations and the text you’ve entered into PDF forms searchable, and we’ve added a convenient way for linking to other documents from plain text and Markdown documents via the contextual menu.

They’re calling this a maintenance update. If you check out the full post at the link, I’d call this a bit more than that. I’ve written frequently about DEVONthink here. Not only is it a great piece of software, but the developers are constantly refining it. There is a 150 hour trial of DEVONthink, so you have nothing to lose if you want to put it through its paces.