The update to 11.0.01 was triggered by the discovery of several active "zero-day" vulnerabilities. These were considered as they were being exploited in targeted attacks before a patch was available.
: Files could be stored on Acrobat.com for access across multiple devices. adobe reader xi -11.0.01-
Improved sandbox performance on Windows, specifically enabling Vista-style Open and Save dialogs to work within the sandboxed environment. The update to 11