@stephenawebby: If you had made changes to the theme files without creating a child theme then all the customization will be lost when you upgrade to the pro version.
If you have used Catch Responsive Free as a child theme and have upgraded to the pro version all you need to do is get inside your child theme folder open style.css file and change Template:*text* to catch-responsive-pro or the name of the folder where your pro theme exists. Also you will need to copy the additional CSS you have added to the free theme to the pro theme. This should bring back all your customization you made on your child theme.
I suggest you to back up your theme files before upgrade in case something goes wrong during upgrade.
Let me know if this helps you out.
Kind Regards,
Skandha
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