Staples Inc. said it will acquire closely held Quill Corp., which sells office supplies by catalog, telemarketing and the Internet, for about $685 million in stock. Staples, the world's largest operator of office superstores, said the purchase will add about 1 cent a share to its 1998 earnings before a charge of about $32 million, and will add about 2 cents in 1999. The retailer said it will issue about 30 million shares for Quill, which had sales of $550 million last year. Staples' contract and commercial business, which includes mail-order operations and contract stationer services to large corporations, had sales of about $1 billion, or 20% of its total revenue. Lincolnshire, Ill.-based Quill will retain its name, headquarters and management after the transaction, which is expected to close in the summer. Shares in Westborough, Mass.-based Staples rose 56 cents to close at $22.75 on Nasdaq.