Contact Adobe support @ http://www.adobe.com/support/acrobat/Adobe Reader 8 and Adobe Acrobat 8 End of Support
Support for Adobe Reader 8.x and Adobe Acrobat 8.x will end on November 3 2011
Note: Adobe supports only the most recent major version of Adobe Reader for Linux, which is version 9.x.
End of Support
End of Support means that Adobe no longer provides technical support or distribute runtimes. This policy affects product and security updates for all derivatives of a product or product version (localized versions, minor upgrades, operating systems, dot and double-dot releases, and connector products.)
--------------But to get u your serial, they should do it.