Can't Change this Background to White

Hi, maybe someone here can help me out and get the gray background behind the image to be transparent or white. I am using a plugin called “Embed Any Document”. It is almost perfect – looks great and is responsive – just can’t change the background. It has something to do with the iframe. I’ve contacted the plugin developer and he said the only way would be to modify the jQuery, of which I am unexperienced in. Is there anything else that can be done to fix this, or is there an easy way in the jQuery that you could guide me through? This is driving me crazy.

Here’s the url to the page: