This is not possible and has a low probability of being added as it conflicts with the primary purpose of an enterprise document management system which is the main purpose of Mayan EDMS.
A primary enterprise feature of Mayan EDMS is its role based access control system. This system is a requirement in enterprise environments where authentication, authorization, access control, auditing, and accountability are basic requirements.
Allowing anonymous access to documents would require dispensing with these features.
If you require this feature, then it is very likely that your real need is for a file sharing system such as a a web based file manager or a content management system (CM) and not a document management system (DMS).