From the Adobe Product Security Incident Response Team (PSIRT):
Today, a Security Bulletin has been posted in regards to the April 13, 2010 quarterly security update for Adobe Reader and Acrobat. The update addresses critical security issues in the products. Adobe recommends that users apply the updates for their product installations.
With this quarterly update, we are enabling the new updater first shipped in a passive state with the October quarterly security update. For more information, please refer to the Adobe Reader blog.
The Security Bulletin: http://www.adobe.com/support/security/bulletins/apsb10-09.html