Preheat oven to 350ºF if using a metal baking pan (or 325ºF/160ºC if using a glass dish).
Line a baking dish with parchment paper, leaving enough excess paper on the sides to use as handles.
In a bowl, combine graham crumbs with pumpkin spice. Add melted butter. Stir until the mixture looks like wet sand.
Pour the mixture into a parchment-lined baking pan. Spread it out into an even layer. Press the mixture down firmly to create the base of the cookies.
In a bowl, combine condensed milk with the pumpkin pie filling. Pour the mixture evenly over crumb crust. Tilt the pan to get an even coating across the Graham cracker base.
Randomly sprinkle pecans (or Rice Krispies), chocolate chips and coconut over the condensed milk layer, then press the toppings down firmly with the flat side of a spatula.
Bake in preheated oven for 25-30 minutes, or until the top is lightly golden brown.
Set the pan on a wire rack and allow to cool completely.
Use the parchment paper "handles" to lift the cookie out of the pan, and place onto a cutting board. Cut into 16 bars and store loosely covered at room temperature.
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Notes
If you're making these pumpkin cookie bars for someone who has a nut allergy, substitute the pecans for pumpkin seeds (if they are nut-free) or puffed rice cereal (Rice Krispies).
The texture of these cookie bars becomes firmer once they cool down.
Allow the cookie to cool completely (1.5-2 hours at room temperature or 1 hour in the fridge) before cutting. This will make it much easier to cut the cookie into bars.