According to my student, Immanuel Kant took time out of his busy schedule of contemplating metaphysics, ethics, morality and epistemology to 'devise the principle that public relations practitioners must fulfil a moral obligation'.
As a public service, here's a handy timeline:
Immanuel Kant: 1724-1804.
PR: appeared roughly 1905.
Given that Kant's main moral insight was that actions are either intrinsically right or intrinsically wrong according to one's sense of duty, it seems unlikely that he both built a time machine and wrote a PR code of ethics. Though if he had, I suspect it would be much better than this meaningless one.