PR (mostly UK) means public relations. In the US it would probably be publicity or working as a publicist. As Molly said, sometimes this involves creating a campaign to improve a person or company's public image, but it's also their job to generally communicate with press / the media about that person or company's activities. For example, their new products, offers, a new movie or a musical artist's new album. Examples: He does PR/publicity for Google. I've been working in PR/publicity for 10 years. A PR/publicist just contacted us to offer review tickets for upcoming Broadway shows. (in the UK, 'a PR' can also refer to the person themselves)

PR = public relations. This is often used with companies and celebrities, who are doing something to improve their image.

Public relations