Dirk Gomez and I are working on this feature for the next version of the search package. Basically it will call an external program to convert the uploaded files to text for indexing. There is already a hook in the search package for this, but no external programs are defined to be called.
I will have more information on the exact implementation soon. It will support Word, PDF, XL formats at a minimum, and it should be relatively easy to add new formats.
