The whole purpose of Container fields is to store files or a reference to them so they can certainly store PDF files. They could store an email if you can access it as a separate file.
But there are significant limitations to using container fields in web publishing environment. Mainly, you can't upload a file to a container field through your browser. There is an add on application, SuperContainer that can add that capability, so research web publishing and this add on application before committing to the project.