In a Dutch oven, combine cranberry juice and sugar. Bring to a full rolling boil over high heat, stirring constantly. Stir in pectin. Boil for 1 minute, stirring constantly.
Remove from the heat; skim off foam. Carefully ladle hot liquid into hot half-pint jars, leaving 1/4-in. headspace. Remove air bubbles; wipe rims and adjust lids. Process for 10 minutes in a boiling-water canner.
The processing time listed is for altitudes of 1,000 feet or less. Add 1 minute to the processing time for each 1,000 feet of additional altitude.