Responsive Iframe Content

I have an lms which contains content inside an iframe - this content resizes, however the text becomes really small on certain screen sizes. I have attached a word doc to show you what happens. I am hoping for a solution, I have a lot of [login to view URL] files so a fix using a stylesheet outside the iframe would be great but if I have to put it inside the iframe I will. I would love this to be fully responsive so people can use on their ipads and iphones without scrolling but have a decent size text to be able to read it. The iframe files were created in a program called ispring. This is an example of the [login to view URL] files - [login to view URL]