Sign Outs can be required for individual sessions using the settings in each session. However, there is an  option to enable a Required Presence Percentage and Required Sign Out for all sessions.

1. From the Home page, click Advanced Options > Settings

2. Click on the Attendance tab

3. Set the Required Presence Percentage to an acceptable amount for the conference

4. Check the Require Users to Sign Out box

5. Check the Overwrite attendance settings on existing sessions box. This will replace the current session settings with the settings defined here. Newly created settings will begin using these newly defined settings as well

6. Click Save