So, When Should You Use This?
Advanced Search is at its most useful, of course, when you are trying to find something squirreled away among a pile of PDF files; you can search them all at one time with a single click.
That being said, I find I use Advanced Search, rather than Find, most of the time, even when I’m looking only in the currently-open document. Using the standard Find command usually has me clicking through many unwanted instances of my target text, looking for the one I actually want; life seems futile enough already without adding to it.
Give Advanced Search a try; I bet you’ll find it indispensable.