Thanks http://support.microsoft.com/kb/2293357

1. Install PDF iFilter 9.0 (64 bit) from http://www.adobe.com/support/downloads/detail.jsp?ftpID=4025 (http://www.adobe.com/support/downloads/detail.jsp?ftpID=4025)
2. Download PDF icon picture from Adobe web site http://www.adobe.com/misc/linking.html (http://www.adobe.com/misc/linking.html) and copied at C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\IMAGES\
3. Add the following entry in docIcon.xml file, which can be found at: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\XML
   <Mapping Key=”pdf” Value=”pdf16.gif” />
4. Add pdf file type on the File Type page under Search Service Application
5. Open regedit
6. Navigate to the following location: 
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office Server\14.0\Search\Setup\ContentIndexCommon\Filters\Extension
7. Right-click > Click New > Key to create a new key for .pdf
8. Add the following GUID in the default value
   {E8978DA6-047F-4E3D-9C78-CDBE46041603}

• Restart the SharePoint Server Search 14
• Reboot the SharePoint servers in Farm
• Create a Test site (with any out-of-box site template) and create a document library upload any sample PDF document(s).
• Perform FULL Crawl to get search result.

Edit this file :

C:\FASTSearch\etc\config_data\DocumentProcessor\formatdetector\user_converter_rules.xml

Add this :

<ConverterRules>
    <IFilter>
        <trust>
            <ext name=”.pdf” mimetype=”application/pdf” />
        </trust>
    </IFilter>
    <MimeMapping>
        <mime type=”application/pdf”>PDF File</mime>
    </MimeMapping>
</ConverterRules>

Run psctrl reset to reset all currently running item processors in the system.