iOS 7.1 Exchange PDF viewing
So we found a workaround via https://discussions.apple.com/message/25159423?ac_cid=op123456#25159423 

"Interestingly, I think I stumbled on a workaround.

For one of the emails with an attached PDF that I have been having trouble with, if I tap on the PDF icon to download it, and then tap on it to open it, I get the error (black or white screen).

But, with this same email, if I first tap on the "Download Full Message" link at the bottom of the email, the PDF will then open correctly when I tap on the PDF icon.

I confirmed that this works on two different iOS 7.1 devices."