hi Michael, my understanding is that epub/pdf versions are only available if you buy the book, not as part of the subscription.
otoh as a subscriber, I think the website doesn’t let you buy the book 
the last time this question arose, the advice was to email support@razeware.com and they’d arrange for the purchase. Who Loves PDF Books? We Do — Again! | raywenderlich.com - #6 by katiecollins