PDF Icon not showing in SharePoint 2010 Document Library
Follow the steps below to resolve the issue of the PDF icon not showing up in Document Libraries in SharePoint 2010:
1) Download icon –
http://www.adobe.com/images/pdficon_small.gif and copy to C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\IMAGES
2) Navigate to C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\XML – Open the file “DOCICON.XML” in notepad
3) Enter a Mapping key <Mapping Key=”pdf” Value=”pdficon_small.gif” /> right above the </ByExtension> tag. Save the file and exit
4) Perform iisreset /noforce
5) Do the above steps in each SharePoint server in your farm.