title: How can I keep my PDF files from appearing in search engines?
body: <p>I am trying to sell ebooks on my website.  The ebooks are in the form of PDF files.  The customers pay to download them with Paypal.  But if I type the beginning of the ebook into the google search the PDF file comes up.   Anyone can then open the PDF file.  I have tried this on someone else's computer and the same thing happens.   </p>
  
  <p>Thus, the question is, how can I keep my PDF files from appearing in Google and other search engines?</p>