Acrobat Reader 11: Fix “There was an error opening this document ..

An error may appear that says “There was an error opening this document. Access denied.”

1. From Acrobat Reader, select “Edit” > “Preferences“.
2. Select “Security (Enhanced)” on the left pane.
3. Uncheck the “Enable Protected Mode at startup” box.
4. Select “Yes” to the prompt about being sure about making this change.
5. Click “OK“.