Pop the popcorn according to the package instructions. Spread the popcorn on a parchment-lined baking sheet, discarding any unpopped kernels. Place one cup of caramel baking chips in a microwave-safe bowl. Microwave in 30-second intervals, stirring after each, until the mixture is melted and smooth. Transfer to a resealable plastic bag and snip the corner with scissors. Drizzle the caramel over the popcorn and immediately sprinkle with 1 teaspoon pumpkin pie spice. Let the coated popcorn stand until the candy is set, about 15 minutes. Break the popcorn mixture into pieces using a wooden spoon or your hands. Sprinkle with 1 additional teaspoon pumpkin pie spice. Transfer to a serving bowl. Store leftover popcorn in an airtight container.