little trick to show a file type icon for any links that point to a particular type of file From: https://plus.google.com/+DavidGilbertson/posts/DY4ktjxuYaV

filetype.css

a[href$=".pdf"] {
  background: url(../img/pdf_icon_16x16.png) no-repeat;
  padding-left: 20px;
}

...or if you don't want to use an icon, but do want to let your users know you're linking to a file:
a[href$=".pdf"]:after {
  content: " (PDF)"
}