Line a large baking sheet with foil and spray lightly with cooking spray; set aside.
In a large bowl, combine popcorn (remove any unpopped kernels), marshmallows, pecans, cereal, pepitas, dried cranberries and pumpkin spice mix.
Place chopped chocolate in a microwave-safe bowl and heat in microwave 1 minute. Stir to melt; microwave an additional minute. Stir until chocolate is melted and smooth. Pour melted chocolate over popcorn mixture. Mix until well coated and spread in an even layer into prepared pan. Cool at room temperature until firm (or refrigerate). Cut into squares to serve. Store in an airtight container.