How to center the google docs in an iframe?

I have developed a website with google docs as pages in the iframe. Also i have added a feedback form made with Google Forms to it. Here is my website for your refrence.

The feedback form correctly got aligned to the iframe. But, the google docs sticks to the left. How to bring it to the center without affecting the rest of the elements?

I have used HTML, CSS and some scripts for notification service and animation.