PR vs promo

PR and promo both are nouns.

Word	Noun	Adjective	Verb	Adverb
PR	Yes	No	No	No
promo	Yes	No	No	No

As nouns, promo is a hypernym of PR; that is, promo is a word with a broader meaning than PR:

PR: a promotion intended to create goodwill for a person or institution
promo: a message issued in behalf of some product or cause or idea or person or institution

Other hypernyms of PR include packaging, promotion, promotional material, publicity.

PR (noun)	promo (noun)
a promotion intended to create goodwill for a person or institution	a message issued in behalf of some product or cause or idea or person or institution
a self-governing commonwealth associated with the United States occupying the island of Puerto Rico