Yes, use the following:
a[href$='.pdf'] { display:inline-block; padding-right:20px; background:transparent url(http://sitename/local--files/pagename/filename.gif) center left no-repeat; } The padding might need some playing with as the distance between the link and the icon will depend on the size of the icon you have saved. One site that has suitably-sized icons ffor download for different file types is here and that page also has a good explanation of the syntax.
Rob