MENLO PARK, Calif.,, Sept. 14—The fourth-quarter hiring outlook for marketing and advertising professionals will remain little changed from the third quarter, according to The Creative Group Hiring Index for Marketing and Advertising Professionals. Ten percent of marketing and advertising executives interviewed said they plan to increase staff levels in the next three months, while 7 percent anticipate declines, resulting in a net 3 percent increase in hiring activity. This compares to a net 6 percent increase in hiring projected....