That is a windowed element that you have no control over. If you want to change a size of a normal pop up window, you got window.resize(), but browsers now a days have an option to block windoww.resize. Best to just use layers (divs) withs display = "none" and display="block" which will show and hide them.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com