DocRead uses the SharePoint API to get the list of users that have been assigned to a DocRead audience. Because of limitations with this API DocRead audiences can only contain individual windows users, SharePoint Groups, ASP.Net roles, standard Windows security groups and SharePoint audiences. Active Directory Universal security groups and distribution lists are not supported.
Also please be aware that, if you configure DocRead to support SharePoint Audiences on a specific site, you will only be able to assign SharePoint Audiences and SharePoint groups to DocRead Audiences on that site, windows users and Active Directory groups would need to be nested inside SharePoint groups. This is due to limitations with the SharePoint audiences control used by DocRead (People Picker).