We are a print shop, similar to how Kinkos won’t sign an NDA to print your files, we generally won’t as well. The only thing we will do with your files and information (as listed in our terms and conditions), is print your game.
When do you make an exception?
If it’s from a big company or a well known brand, we might sign an NDA, but in general, it’s not worth our lawyer’s time to review and advise on small print jobs, where our profit is minimal. We believe that our terms and conditions will cover the majority of print jobs. We have all our employees sign NDAs as well, to better protect your projects as well.
Here are a few threads from different places that refer to playtesting games and NDAs, and this is the general consensus from the internet people: