Bob John Robison has been appointed director of Hill and Knowlton's Washington office.

Joseph V. Arcaro, director of display advertising for The Washington Post, has been awarded the 1981 Silver Medal by the Advertising Club of Metropolitan Washington, the organization's highest honor. Arcaro joined the retail advertising staff of the Post in 1950. He was promoted to assistant retail advertising manager in 1962 and named retail advertising manager in 1969. He became director of display advertising in 1979.

G. Richard Booth and Marshall S. Jorpeland have been named account executives for Robert H. Kruhm & Associates, an association publication and exhibit marketing firm.

Paula Christie and Lucy Erdelac have been promoted to account supervisers at the advertising and public relations firm of Henry J. Kaufman & Associated Inc.

Ronna Freiberg, former White House special assistant for congressional liaison in the Carter administration, has joined the public relations firm of Gray and Co. as an account supervisor.

Paul Hines has been named managing editor of Army Times. Hines joined Army Times Publishing Co. in 1979 as news editor of The Prince George's Journal. He joined the Army Times as an associate editor in 1980.

David J. Umansky has joined the public relations firm of Jackson/Summers Associates Inc. as an associate. He was previously director of public affairs and consumer participation for the National Highway Traffic Safety Administration.

Rachel Greenberg has been promoted to senior planning associate for the public relations and issues marketing firm of Porter, Novelli & Associates Inc.

Andrew E. Manatos, former assistant secretary for legislation for the Commerce Department, has joined the public affairs and public relations firm of Fraser/Associates as senior vice president. Mike N. Manatos, former director of government relations for Procter & Gamble, joined the company as senior consultant.