The Mysteries of SharePoint Search
There's a myth in town. SharePoint searches documents. While the search feature of the SharePoint products is a key element, it's not entirely true that it actually does any searching. Walk with me on this one.
SharePoint, like a conductor in an orchestra, really just orchestrates a search request. As a conductor doesn't play an instrument, SharePoint doesn't actually do the mechanics of a search, it just makes the request. It's really all about IFilters and the search capabilities they provide. The SharePoint search pages, object model and web services are just facades to access the real workers.
This conversation came up because, out of the box, SharePoint only searches the following content types: .txt, .htm, .doc, .xls, and .ppt. And this search is not SharePoint but rather SQL Servers full-text search engine. After all, a binary file type (like PDF) can't really be searched unless the searcher knows how to read the format. SQL Server knows how to read the base types and with the addition of new iFilters, you can extend that. You can get additional IFilters for PDF, RTF, MSG, ZIP and other formats from various sources (Microsoft has a few free ones like for RTF). A good source of commercial IFilters is the IFilterShop.
So next time you try searching for content check to make sure your SQL Server (all content for SharePoint is stored in SQL) has an IFilter that recognizes the format you're looking for. Also a catch is when you do need to add a new search type, make sure you install the IFilter on the SQL Server and not the SharePoint one as it's the mechanic that's actually performing the search and just providing results to SharePoint to present to the user.