The simple WAIS search engine that FP uses isn't really capable of scanning
inside of PDFs and Word documents. That is actually far more complex because
those aren't plain text documents like web pages are. You'll need to go up
to a more robust solution. There are some out there that are free, such as
Microsoft's Indexing Services, but hosts usually charge a bit more for these
features and it takes a bit of programming to work with them.
Find out what server-side programming technologies your host supports and
that will give you a starting point to look for existing scripts or
applications that you can use in your site to get this additional
functionality.
Hope this helps,
Mark Fitzpatrick
Microsoft MVP - Expression