set default PDF extension for Downloaded Forms - Collaborator

Is there a way of making .PDF the deafult file extension for downloaded forms?

I'm trying to dteremine if this feature is controlled by the actual subscription type pr the access type.

I have a Basic User Account setup as a Collaborator on a form which I author under a Plus subscription. I would like the default file type to be .PDF for any forms that are saved with their own unique name. However, unless I include the .PDF as part of the file name, the file saves without an extension.

Is there a way that I can set this as a default for the Collaborator because having to remeber to add the file extension is a pain.