Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente; drain and transfer to a large bowl, reserving 1 cup pasta cooking liquid.
Meanwhile, cook pumpkin purée, cream, paprika, 1 ½ tsp. salt, and ¼ tsp. pepper in a large skillet or wide heavy pot over medium heat, whisking constantly, until smooth and warmed through, about 3 minutes. Add ¾ cup pasta cooking liquid and whisk to combine. Add pasta and ¼ cup parsley and cook, adding more pasta cooking liquid to thin sauce as needed, until heated through, about 1 minute. Season with salt and pepper, then transfer to a platter. Top with more parsley and black pepper and serve.
