The print at home option is new for 2015 and is currently being implemented by the various resellers. It's not available yet for all pass types and resellers, and indeed it's not available for the Swiss Travel Pass Flex yet. If you order through the Swiss Railways webshop they can have the pass sent to your hotel in Switzerland, if that's convenient to you (pick a different billing and delivery address while ordering). That takes 2 to 3 working days depending on which shipping option you pick, so that could be an option for you. All the purchase options are listed here.
Enjoy your trip!