Big fan of rga! I use it almost every day for the academic part of my life, when I want to know the location of some specific keywords in my lecture slides, books or papers I've been reading. Even for single ebooks, it is often more useful than the search in Acrobat Reader.
The search in PDF viewers is an anti-feature in terms of UI and performance. Their advantage is that they allow to scroll to and highlight the found phrase back in the document.
