Don't know if you can actually search the documents once they're in the database, since it's all binary info in there (i.e. no text). One option is to add a field with "keywords" and put Full-Text on that so the column is searchable. THen, when the user searches, you search for the full-text field (keywords) and if there is a match, then you return a link to the PDF/MSDoc file.
I know google has something like that where it can search PDF files, but I don't think they're stored in a DB.
~Brett