Article 2: Display PDF icons to PDF documents in a SharePoint Library

Go to folder with path “C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\IMAGES” then copy pdf.gif and paste to here

After you copy the picture file you need navigate to “C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\XML” then edit file in notepad

And edit the DocIcon.xml with notepad and add the line

Add an entry to support PDF files.

<Mapping Key="pdf" Value="pdf.gif"/>

You must reset iis by click start | run then enter iisreset

Open document library, you will see icon pdf with document file is pdf