Combine pears and orange juice in a large Dutch oven. Stir in orange zest, cinnamon, nutmeg, cardamom, and vanilla bean seeds. Bring to a boil. Cover, reduce heat, and simmer until pears are tender, 45 minutes to 1 hour.
Puree pears in a food processor or using a food mill. Return pear puree to the Dutch oven. Stir in sugar until dissolved. Cook and stir over medium heat, uncovered, until thickened, 30 to 40 minutes.
Inspect 10 pint jars for cracks and rings for rust, discarding any defective ones. Immerse in simmering water until pear butter is ready. Wash new, unused lids and rings in warm soapy water.
Pack pear butter into hot, sterilized jars, filling to within 1/4 inch of the top. Run a clean knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe rims with a moist paper towel to remove any residue. Cover with metal lids and screw on rings.
Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars 2 inches apart into the boiling water using a holder. Pour in more boiling water to cover jars by at least 1 inch. Bring to a rolling boil, cover, and process for 5 minutes.
Remove the jars from the stockpot and let rest, several inches apart, for 12 to 24 hours. Press the center of each lid with a finger to ensure the lid does not move up or down. Remove the rings for storage and store in a cool, dark area.
