Toss pecans, brown sugar, and pumpkin pie spice together in a bowl.
Melt butter in a skillet over medium heat. Cook and stir pecans mixture in hot butter until lightly toasted and fragrant, about 5 minutes. Spread candied pecans out onto a sheet of waxed paper; cool completely.
Arrange 32 gingersnap cookies in a single layer over the bottom and up the sides of a 2 1/2-quart serving bowl.
Beat pumpkin puree and cream cheese together in a bowl with an electric mixer until smooth and creamy; add vanilla extract and pumpkin pie spice.
Whisk milk and vanilla pudding mix together in a bowl until pudding mix is completely dissolved and mixture is well-blended, about 2 minutes. Let pudding stand until slightly thickened, about 5 minutes. Fold in 1 1/2 cups whipped topping. Stir pumpkin mixture into pudding mixture.
Spoon 1/2 of the pudding mixture over the cookies into the prepared serving dish. Arrange remaining gingersnap cookies over pudding mixture. Spread remaining pudding mixture over cookies and spread remaining whipped topping over pudding mixture. Sprinkle candied pecans over the top.