There’s really no way to do that. As soon as someone views a page on your site, a copy is downloaded to their local computer in the browser cache. So you don’t have control over that.
Sorry to be a pest, but in the end I solved this issue. Yes, you can stop your audence from printing content.
In your style.css file place this code.
/* Print Style Sheet */
@media print {
body { background:white; color:black; margin:0 }
#header { display:block }
#content { display:block }
#comments { display:block }
#sidebar { display:block }
#footer { display:block }
}
This is just one way to do it.