Cook pasta: Boil fettuccine to al dente per package directions. Reserve a bit of cooking water, then drain.
Make sauce: Heat olive oil in a skillet over medium. Add garlic and sage and sauté until fragrant.
Add pumpkin: Stir in pumpkin puree and milk. Simmer gently and whisk until smooth, letting it thicken slightly.
Finish sauce: Add Parmesan, then season with salt and pepper. Whisk until creamy.
Combine: Add drained pasta to the sauce, tossing to coat. Use reserved pasta water to thin as needed. Serve hot, topped with more Parmesan or toasted pumpkin seeds.