Bring a large pot of lightly salted water to a boil. Cook linguine at a boil until tender yet firm to the bite, about 11 minutes; drain.
Heat olive oil in a large skillet over medium heat. Add onion; cook and stir until translucent, about 5 minutes. Stir in cumin and Cajun seasoning until fragrant, about 1 minute. Add sausage; cook and stir until browned, about 5 minutes. Stir in pumpkin and cook, stirring occasionally, until heated through, about 3 minutes.
Pour Alfredo sauce and milk into the skillet; cook, stirring well, until sauce is hot, 5 to 10 minutes. Add linguine and toss to coat with sauce. Serve garnished with Parmesan cheese.