I'm a big fan of BareGrep Pro by
Bare Metal Software, a truly excellent visual grep. I didn't expect much when I downloaded the freeware
Hound from
Jimmy the Fork. Indeed it won't replace BareGrep Pro. But I was impressed when I turned it loose on a directory that happened to have some PDFs in it, and found Hound's status bar saying things like "Examining PDF", "Converting PDF to plain text," and giving a grep-like posting. I don't know how it does it, and didn't check for absolute accuracy, but the set of results it gave looked right.
Nice bit of humour on that site, too. E.g., his duplicate file finder is called Dolly, with a picture of a sheep