Ok. From what I can tell, this is a security fix that was introduced in 11.0.06 and messed up Adobe Reader functionality.
The PDF I have tested require file attachments.
I can get around the error by:
- Opening Adobe Reader.
- Edit-->Preferences
- Security Preferences
- Uncheck the "Enable Protected Mode at Startup" checkbox (which is checked by default when installing 11.0.06 or greater)
This sucks lemons. Now I have to tell people to reduce security settings in order to attach files. (really?)
I sure would like to know if there's a better solution.