Thanks for the links… I tried your site and pages in this to simulate iphone and ipad: http://www.responsimulator.com/ and everything worked well for me. I also loaded up your site in my iphone, and everything appears to be working well there. Your PDF’s open in a new window and it looks like it’s hosted by ISSUU ?
Overall, I wasn’t able to replicate what you are experiencing. You mentioned that it doesn’t happen all the time, so I’m thinking it must be something else that might be causing the issues you mentioned, but not sure what, other than a much older browser and version?