In an attempt to Add PDF icon to the search results I had to edit the DOCICON.xml file which is located at C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\XML
If you make any errors or do not close your mapping keys off properly your search results will be corrupt and no longer show any search result icons.
TIP - If you have just added the PDF document to the DOCICON.XML make sure there isn't already the same entry as this will also cause the file to corrupt.
