Xerox Corp., the multibillion-dollar office automation and insurance company, announced yesterday that it intends to sell all of its publishing subsidiaries for $500 million.

International Thomson Organization Ltd., a Toronto-based multinational conglomerate with interests in publishing, travel and oil, will acquire R. R. Bowker Co., University Microfilms International and AutEx Systems through its U.S. holding company.

New York-based R. R. Bowker is best-known for publications that include Books in Print and the trade journal Publishers Weekly.

University Microfilms International, an Ann Arbor, Mich., firm, provides bibiliographic information and text copies of publications, books and doctoral dissertations. AutEx Systems, located in Wellesley, Mass., operates computerized information networks in securities and other dealer markets.

Gulf & Western Industries Inc., a New York-based multinational conglomerate, will acquire Ginn & Co., which publishes elementary and high school textbooks. Chicago-based Field Corp., a privately held holding company formed last year by Marshall Field V to manage his assets, will acquire Xerox Education Publications, which publishes Weekly Reader and Current Events and has children's book clubs.

The Times-Mirror Co., which owns The Los Angeles Times, Newsday and several other newspapers, will acquire Xerox Learning Systems, which markets training programs. The Times-Mirror Co. said its acquisition price will be in excess of $100 million.

"The decision to sell the publishing group was reached as it became clear that a greater financial commitment would be necessary to stay competitive with the leading companies in the publishing industry and would therefore require diversion of resources from the primary Xerox businesses," said David T. Kearns, Xerox president and chief executive officer.