Hi thanks for your reply.
I am an administrator of our Alfresco system and have been tasked with this requirement. So today I have created a model called 'Default properties', which I have mirrored the properties to exactly how a document that has not had a model applied to it would look. When I first upload a document, I am able to select 'Change Type' and it gives me the option of both models/types we currently have, however, if I select the model that has 'Document Owner' etc in it, then try to change the type to the default type that I created, there are no types listed. It is as if once one type has been assigned to a document, that it cannot be removed or changed, which in the event that you apply the wrong type to a document, that you must delete the document and then re-upload it again to be able to change its type again.
So in the event that I am unable to create a type and assign it to the document in the scenario above, are you able to advise how as an admin I would be able to do this through the java console?