With EInk displays, scans also work well - see for example
BeBook font sizes and types. I don't know how well this works with the jetBook, and you obviously need a scanner (I used a HP All-in-One printer).
As an aside, the fact that the Kindle is the only Reader to include a screenshot capability is an indication that it is the only device used stand-alone (i.e. outside a test harness) by its developers. I don't know why the jetBook does not include this capability. It can be hard to implement "on demand" (i.e. within the reading app), as done on the Kindle, but it is very easy to implement with (say) a 30 second delay so that it can be invoked before opening up an ebook.