Thinks to think about
1. You are creating an annot in a CosObj. To add this to a page you'd use PDPageAnnAnnot. PDPageAddNewAnnot creates the CosObj itself.
2. There may be other required keys in an annotation which you will have to provide because you aren't using PDPageAddNewAnnot
3. PDAnnotNotifyContentDidChange is an important method but you pass it a dictionary key, NOT the annotation type.