Papillons do not recognise their small size, nor their vulnerability; they think of no difference between them and a Golden Retriever, Shepherd, or other large breed. Some of them even will be quite bossy to them, bossy to any other dog.
But if you already have a larger dog at home and you are in the process of adding a little Papillon to your family, make sure to realize your big dogs temperament first:
Is he aggressive, does he like to chase things?
If he does, be aware, he may use your little dog as a prey animal, thus endangering your small dog.