There is a bug that is affecting many iPhone/iPad users who also have an Exchange account setup in the Mail app, where after updating to iOS 7.1 or 7.1.1 attachments can’t be opened.
This is most commonly reported with PDF attachments opening as a black white or black screen. If Adobe Reader is installed, the user may additionally get a report that the file is corrupt or damaged. This bug also affects other types of attachments, including JPEGs and Word documents.
Almost all of the people experiencing this bug are connecting to Exchange 2007 servers.
In many cases, if the user scrolls down to the bottom of the email, and clicks the “Download Full Message” link, the attachment will display properly. This unfortunately doesn’t work for all attachments.
If the user accesses their Exchange account using Outlook on a workstation, or via the OWA web interface from either a workstation or their iOS device, these attachments open fine.
Some have reported this problem only occurs when receiving attachments while connected to cellular, and that it doesn’t occur when receiving attachments while connected to a WiFi network.
If the user forwards an attachment that isn’t opening properly from their iOS device, it will be corrupt for whoever receives it.
There are numerous threads on several discussion forums detailing this bug. Apple apparently has been aware of it shortly after iOS 7.1 was released on 3/11/14. People experiencing the bug were disappointed after discovering that iOS 7.1.1 didn’t fix it, and some have reported that this problem actually became more prevalent after updating to iOS 7.1.1. Here is a thread I have been monitoring daily since this issue came to my attention: https://discussions.apple.com/thread/5992793