How to make sure that the portable firefox instance always uses the pdf viewer plugin within the portable app configuration?

As I have been using and testing an app I am building for myself to make use of a instance of firefox portable, I noticed recently noticed that the Adobe PDF Plugin being used was that of whatever the local PC I was plugged into was using. I had thought since I provided the plugin and setup the portable firefox instance with a specific plugin for PDF, it would use the one I provided.

What is required in terms of files, configuration, etc for a portable firefox app to insure that it always uses the Adobe PDF plugin I want it to use?

The main reason is because for the content I am using this app for, Adobe PDF Reader plugin v7 and v8 both crash firefox. So I want to make sure it is always using v9.

Thanks...

John