Enterprise users can create a backup copy of their form specifications (i.e. the questions and logic, etc, that make up the form) by using the Export xform command on the Design tab (xform is a common format used by many form-based data collection systems).  This provides a backup copy that can be reimported into the system if a user accidentally deletes a form.

Note that backing up a form specification to xform is not the same as backing up the form's data.  A backup of collected data can be accomplished by using the Export command on the data tab.