Just came across this search engine for PDF, DOC and PPT files. It is called http://www.osun.org/
For example, lets say you wanted to see what PDF files are available that include the words ‘ revit families’. Have a look at the results by following the link below:
http://www.osun.org/revit+families-pdf.html
This could be a very useful site for quickly searching for quality data. If Google can’t find what you are after, give this site a go.