Thanks for asking.
Pro is our new theme that is available along with X. https://theme.co/pro/7
The main difference between X and Pro is the addition of the header and footer builder. These powerful new builders allow you to have complete control over the design of your headers and footers with multiple different elements. They also allow you to assign unique headers/footers to each page/post if required. If you would like to to know more I would suggest you to take a look at Pro launch post:
If you would like to convert your existing site to Pro, I recomend you to refer our X to Pro conversion guide:
As mentioned, Pro comes with Header and Footer builder tools. Please take a look at following article and video tutorials to get started with header and footer builder:
However, please note that after converting X Theme licence to Pro, you can't rollback.