A Nashville-based public relations and marketing firm is merging with a Jacksonville, Florida-based firm to create Nashville’s fourth-largest PR and advertising agency, as measured by revenue. The Bradford Group, an agency specializing in PR, social media and content marketing, announced plans to merge with the Dalton Agency, a full-service advertising and PR agency, to expand its services and staff size. “It has been a goal of our agency for some time to expand both our geographic reach and…