Google still has the best ranking. Indexes PDFs and word documents.
Push services for Google are available at Google Alert.
A special service is available with Google Scholar. It shows for catch words or names the refering documents in the web and in paper editions.
Alternative to Google, with Yahoo!-Index.
same index and ranking as Bing, but more privacy and icons for results as recommendations.
Meta search engine with a good ranking and refine your search-Option.
German meta search engine.