I developed a web site with Mezze and then decided to purchase Mezze Pro, but when I activate Mezze Pro it doesn’t use any of the original layout and content. I don’t want to re-create the website again, I just wanted to upgrade the theme. How do I do that?
The data/content that you have added in the free version of the theme will work fine even when you update the theme from free to pro.
However, the settings that you previously specified in the customizer of the theme will no longer be there as in pro version of the theme, you will get a fresh customizer and you should setup the settings manually.
Alternately, you can also add the given snippet below in the child theme of your pro theme which will get the customizer setting that you specified in the free theme.