Updating the pro version is simple.
First download the file from your account. Be aware that the updated file is the original file. It has just been reloaded with the new version. Then unzip it and install it as though you were installing AwoCoupon for the first time, through the Extensions->Install/Uninstall interface in the joomla admin screen. And no, your data will not be lost, it is all preserved through the upgrade.
With that said, it is still good practice to backup your data before updates.