With more digging, I have found out that you also need to assign permissions of that folder. Simply sharing a file to someone outside the project (client) in itself will not suffice (from what I can see anyway).
With that in mind, you can only assign permissions to folders and not files within those folders. So, say you want to share a single file within a folder to someone outside the project, then you will have to assign permissions to the whole folder, which to me doesn't make sense. You want to be just able to share a file with someone who gets a link to open and view, and maybe print. This is how it works with all many could based services.
Also, to assign permissions to someone outside the team so they can view a folder, they will need an Autodesk Account (which is basic to set up in fairness).
Has anyone any thoughts? Am I missing something, or am I on the right track?