PDF Icon In Moss (Sharepoint 2007)
moss doesn't install an icon for pdf document type file by default . inorder to
install the pdf icon into moss you should follow the following stips :
1) right click to download image 
2) save the icon to (C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\template\images) and rename the file to icpdf.gif
3) open the file docicon.xml you should find it here : C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\template\xml\docicon.xml
4) add a new mapping key
<Mapping Key="pdf" Value="icpdf.gif" />
5) save the file docicon.xml then restart IIS (iisreset /noforce).
and now you can see the pdf icon for all the pdf documents within your portal .