Document the requirement that the IBM Cognos Dispatcher must be configured to trust the Gateway certificate in order for dynamic imagery to render via PDF (as well as other embedded imagery formats such as Excel 2007 format).
In order for dynamic PDF images to render with IBM Cognos, all IBM Cognos Dispatchers must be configured to fully trust all (SSL/TLS) certificates hosted by all IBM Cognos Gateways/Load Balancers/Reverse Proxies as documented in IBM's documentation here: <a href="http://www-01.ibm.com/support/docview.wss?uid=swg21339916" target="_blank">http://www-01.ibm.com/support/docview.wss?uid=swg21339916</a>. Contact IBM Cognos support for assistance in establishing trusts between Cognos Gateways and Cognos Dispatchers as documented in the preceeding IBM KB.