I'm afraid not. You cannot upgrade from Acrobat 6 Standard to Acrobat 11 which is more than 3 versions back. You can only upgrade from Acrobat 8, 9 and 10 to version 11.
Please contact Adobe Sales support to check if there are any current offers available to purchase the latest version.
You can also check out Creative Cloud - creative.adobe.com which is a subscription. Creative Cloud is one of the milestone of Adobe!
Thank you for your answer.
What about upgrading from version 6.0 to 8 or 9?
2013/2/21 JairajMike <firstname.lastname@example.org>
Re: Upgrade created by JairajMike<http://forums.adobe.com/people/JairajMike>in
Downloading, Installing, Setting Up - View the full discussion<http://forums.adobe.com/message/5090420#5090420