Make Your PDFs Work Well with Google (and Other Search Engines)
http://www.acrobatusers.com/articles/2006/02/pdf_for_google/pdf_for_google.php

Johnson, Duff
Adobe
2006

Abstract:

In Google's search results, and in the results of most other search engines, the listings of most PDF files appear at best unprofessional, and at worst, downright embarrassing.