Preheat oven to 350 degrees F.
Line a baking sheet with aluminum foil and set aside.
Remove seeds from one medium-sized pumpkin and place in a large bowl. Pour water over the pumpkin seeds and separate seeds from strings. Discard strings and remaining insides of pumpkin.
Drain seeds in a fine strainer and pat seeds dry with a paper towel.
Place seeds on prepared baking sheet and drizzle olive oil over seeds. Stir seeds around until coated with oil. Using a spatula or the back of a wooden spoon, pat the seeds down around all edges of the baking sheet to get them in one layer as much as possible.
Sprinkle with Cajun Seasoning.
Bake in oven for 10 minutes, then remove from oven. Stir the pumpkin seeds and again, pat the seeds down around all edges of the baking sheet to get them in one layer as much as possible. Place back in the oven. Bake 10 more minutes. Remove from oven and let cool on baking sheet for 5-10 minutes.
Remove from baking sheet and serve!