You can't. You'll need someone with CC to save them as IDML files.
Yep, the answer is no. So, I just spoke with Adobe Customer support. When you read CC files back into CS6, all the work done outside of the artboards is lost. And they are saying there is no way to convert and no way to extend my trial. So they basically require us to pay them to get our work back.
Here was our correspondence:
(I asked about the issue above)
Kabir: Hello! Welcome to Adobe Customer Service.
janna renner: hello
Kabir: Hi Janna.
janna renner: did you see the question i typed in on the previous screen?
Kabir: Yes! I received that.
janna renner: great.
Kabir: Allow me 1-2 minutes while I read that and help you.
janna renner: sure
Kabir: Thank you for your patience.
Kabir: Janna, it is not possible to use the trial again on the same machine or using the same Adobe ID, If you wish to use the trial again then you will have to install it on the second machine with a different Adobe ID.
janna renner: this seems like a huge hole in the process. So unless i have a second computer, I've lost all the work I did outside of artboards in creative cloud?
janna renner: is there any way to convert the file outside of adobe?
Kabir: We request you to post your issue in Adobe forums, so that you will receive support from Adobe experts.
Kabir: Please refer this link for Adobe forums : http://forums.adobe.com/index.jspa?promoid=DJGWK
Kabir: Support for this product is available through Adobe forums.
janna renner: i'm not saying this is your fault, but now Adobe wants me to search the forums for a solution?!
janna renner: There is no one who has the authority to extend a trial just one day?
Kabir: Janna, I am really sorry to inform you that it is impossible to get the trial for more the 30 days.
janna renner: Man, Adobe is KILLING me, Kabir
janna renner: i'm sure this issue has come up for others. they don't give you any specific solutions to point us to?
Kabir: Janna, I truly understand your concern. However it is not possible to get the trial after the 30 days in the same system with the same email address.
janna renner: i know you can't give me any more info. i'm just sort of in shock about this. is there anyone else i can contact about this issue?
Kabir: And since Adobe doesn't support the trial via live chat. You need to refer the forum. Since the support for the trial version software is only available through the Forum.
janna renner: so they want me to pay $30 to get my own work back. just put some boogers on the CEO's sandwich for me, OK?