publicist; propagandist
Refers to a person whose role is to disseminate information, promote an organization or cause, or shape public opinion. The nuance ranges from neutral publicity work to more charged propaganda, depending on context.
He is promoting new products as a publicist for the company.
戦時中、政府の宣伝員が国民向けの情報を流していた。
During the war, government propagandists disseminated information to the public.