I had a client that was doing a similiar thing, but wanted the ability to be able to index documents by user-defined name/value pairs.
They were using a imaging server called Alchemy ([link|http://www.onetouchgt.com/alchemy.html|http://www.onetouch...alchemy.html], I believe). I do believe it came with client software, as well, that handled the scanning and indexing, and would then store to a central server.
It also had APIs, as well, which enabled my company to build a web interface around their document repository, including searching capabilities.
It was fairly nifty. You might take a look at that.
HTH,
-Jason