You may want to add the following to the get_form_initial
method of your wizard:
from django.core import exceptions
class DocumentWizard(SessionWizardView):
# ...
def get_form_initial(self, step):
# ... determine document_id
document = Document.objects.get(id=document_id)
if self.request.user == document.owner:
document_dict = model_to_dict(document)
return document_dict
else:
raise exceptions.PermissionDenied