Should you decide to get Jing Pro, it's your Screencast.com account that is tied to Jing's "Pro-ness". In other words, if you bought Jing Pro with "JingUser@mail.com", and then change the Account in More > Preferences to an account that is not associated with Jing Pro, Jing will restart and revert back to the free version. Re-enter your Screencast.com account you used when you bought Jing Pro to get the Pro features back.
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=Includes video tutorial