Like many things with Upverter...there's probably a way to do what you want, but the documentation is so poor (and the support pretty much non-existent) that I was unable to figure it out. I tried at length to import a dxf to use as my pour areas, but despite numerous emails to support I can't figure it out and they're not helping. Support and responsiveness from Upverter has pretty much ceased. My recommendation to you would be to use a drafting program to define your pour outline. Keep it with 90 degree corners, no radiused corners. The simpler you can keep your coordinates, the easier it'll be to enter them manually into Upverter. You'll then need to enter them all manually, separately for each layer. I'd love to be proved wrong here if someone can show an easier way.
I too have have stopped my subscription. Now, despite only having a single design...I can't do anything with it other than export gerbers etc. Despite the web info that says you can have two private designs with the Free subscription...that appears to not be the case if you downgrade from the Pro level. So, I feel a bit like I'm being held for ransom. I can't even make any changes to the single design I have unless I pay for another month. Have tried connecting with Zak twice about this but no change.
I love the concept of Upverter and really hope it succeeds. Having said that, I'm going to buy an Eagle license this morning.