Just a quick note that foxit software's instructions on adding a pdf icon apply to Sharepoint 2010 just like they did to MOSS 2007: http://www.foxitsoftware.com/pdf/ifilter/installation.html. The only difference is that you do this in hive 14 not hive 12 (ie Drive:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\Template\).