I know there are probably many solutions, but what's the easiest and/or most user friendly way to provide search capabilities across PDF files? I'm thinking of a webpage that links to several PDFs and I want to offer the user the ability to search them all at once.
You should consider a content management system which allows this feature - while many do not include this feature out of the box many of these open source cms engines have vast amounts of useful plugins that can extend the engine to support or type of things.
Using two of the most popular CMS as an example
As I mentioned in the previous paragraph about plugins and extensions its worth while searching various open source content managements with in the plugins sections... for suitable addons.
Joomla PDF extensions that may do the job:
OS PDF Indexer - indexes PDFS and makes them searchable using the JOM Search platform.
PDF Indexer - Allow PDFs to be indexed and searched via the Joomla/Mambo search module. (Joomla 1.5)
Wordpress PDF extensions
There is far to many to list but here is maybe a suitable one which looks good is Google Document Embedder Kinda good if you want some way of easy management of your PDFS never mind the fact that it's stored on Google which is a plus.
There are handfuls of CMS that will do this for you, and if you don't want to use a plugin then you will need to code your own, or find a CMS out of the box that does this. Using Google is your best tool here and use search phrases like "PDF Indexer and Search Wordpress"
Adapting your own platform to support PDF searching
I found some discovered information for you posted on Stack Overflow and it contains various php snippets for extracting PDF text using PDF which should be useful to you, additional they have a link to a blog about reading PDF doc files in PHP which again will be helpful, if you want to read more take a look at Stack Overflows search through pdf files with php
As mentioned in my comment I don't think there is any quick and dirty way of doing this without a heavy amount of coding, you will need to use PHP as I do not think any JS solution exists.