Mac users - any PDF software capable of quickly searching multiple files?

An issue relating to Mac users cropped up in a thread on the UFO & Aliens Forum which I thought would be worth raising in this "Computer Help" forum.

Basically, I recently started a thread (entitled "FAST searching of major free online collections of UFO journals (or just browse/download them)") which discussed the use of one piece of free software (X-Change Viewer) to search all the PDF files in a directory for a keyword (and gave some useful sources of PDF versions of major UFO journals).

However, that specific piece of software is, apparently, limited to Windows users.

A UFO researcher with a Mac computer has asked if I know of a Mac equivalent.

I don't know much about Macs, so wondered if anyone on here had any suggestions for him...

I know Adobe Reader X has a similar function - at least on Windows- but (on my computer...) it seems to be VERY slow relative to X-Change Viewer.

I've done a few quick Google searches, and the webpage below suggests "Skim" for Mac Os users:

blogallalong.com...

It is definitely the best equivalence to pdf-xchange viewer.

But someone else disagreed:

Skim for mac doesnt hold a candle to pdf x change viewer; the number of things the latter can do is amazing. I ended up having to use pdf x-change viewer via a wine layer, which although functional, is not ideal.

(I've never come across a "wine layer" and, since I don't own a mac, presumably never will...)

Has anyone used "Skim" and know if it (or any other Mac PDF software...) has a fast search function allowing users to search directories full of PDF documents for a keyword so I can suggest it as a possibility to the chap that asked for a Mac alternative??

All the best,

Isaac

Any thoughts from anyone, before I report back to the person that asked me about this?