Save, saving a copy to another location, and getting a PDF out.
File > Save saves the open project where it already lives.
File > Save As offers the managed locations:
Each makes a copy of the project at that location and asks only for a name and folder. The project you have open stays open and stays where it is - this is a side copy, not a move.
A destination is greyed out when it is not usable: the location has not been set up, or it is a network location the app currently cannot reach. Cloud is greyed out in every build for now, because there is no cloud destination behind it yet.
File > Save As > PDF… writes the sheets out as a PDF. That is an export rather than a copy of the project, and there is a fuller set of options behind Export Pages if you need to choose what goes into it.
Opening a PDF directly puts you in a quick-look mode, and the File menu changes to match. Instead of the Save As locations you get:
New standalone .idf files are no longer created. Existing ones still open normally; anything new
is a project in a managed location.