Cook penne pasta in salted boiling water until al dente. Reserve ½ cup pasta water; drain and set aside.
Season shrimp with Cajun seasoning.
Heat olive oil and butter in a large skillet over medium-high heat.
Sauté Andouille sausage until browned; remove and set aside.
In the same skillet, cook shrimp until pink and cooked through; remove and set aside.
Reduce heat to medium and melt butter; add garlic and sauté briefly.
Pour in heavy cream and simmer gently.
Stir in Parmesan cheese and smoked paprika until smooth.
Add cooked pasta, shrimp, and sausage to the sauce.
Toss to coat, adding reserved pasta water if needed.
Season to taste and garnish before serving.