There's a current issue with generating PDF and paper bills. This is a technical problem with our billing partner Fuji Xerox and it affects bills generated on 11 October and 15 October. It's being investigated and will be resolved as soon as possible. In the meantime you can contact customer service and they'll be able to provide you a copy of your bill directly.
This isn't likely to be the cause of the original post here though, because it's outside the timeframe affected.