Cook the pasta according to package instructions in a large pot of salted boiling water. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and cook until translucent, about 3-4 minutes.
Add the minced garlic and diced red bell pepper to the skillet. Sauté for an additional 2-3 minutes until the vegetables are softened.
Stir in the Cajun seasoning, paprika, salt, and black pepper, and mix well.
Add the shrimp to the skillet. Cook for 3-4 minutes, or until the shrimp is pink and cooked through.
Reduce the heat to low and add the crab meat, heavy cream, and chicken or seafood broth. Stir to combine.
Gradually mix in the grated Parmesan cheese and let the sauce simmer for 5 minutes until it thickens slightly.
Combine the cooked pasta with the creamy sauce and seafood mixture. Toss gently to coat the pasta evenly.
Serve hot, garnished with chopped fresh parsley if desired.