Currently, there is no converter to change the format from PDF to CDR. I've searched everywhere, but couldn't find anything about it. However, for some CorelDraw versions, you can simply drag and drop the file into a new document. It won't work with all the PDfs, but I've seen users reporting on other forums that they managed this way. Also, make sure that your PDF files are with restrictions set to default and no password is assigned to the file. If you try to open a file that has been password protected, a message will appear or CorelDraw will show you errors.
FoxPDF CorelDraw (CDR) to PDF Converter can only be used for the reversed process, not the one you need.