Pumpkin can be frozen easily. First, cut the pumpkin in half, scoop out seeds and inside stringy pulp, and bake in the oven at 350F for an hour. Larger pumpkins may need more time. When the flesh is soft when poked with a fork, its done.
Separate the seeds from the pulp, save seeds for storing, and save the pulp for making pumpkin syrup.
Next scoop out the flesh from the baked pumpkin. You can now put it in bags and freeze.
For large quantities of pumpkin, especially if it is a watery type, you can strain out the juice before freezing. Using a strainer and a cheesecloth, strain the pumpkin and you should get around 1 cup of pumpkin and 2 cups of watery orange juice from 3 cups worth. The pumpkin flesh can then be stored in freezer, taking up 1/3 of the space it would have.
Next, reduce the pumpkin juice. Add the pulpy bits from when you seeded the pumpkin and reduce them down, too. They hold a lot of juice and nutrients, and pumpkin flavour. When your juice has reduced to a thick, caramel-like liquid, strain it and store the liquid in the freezer.