NEW YORK — Packaging Corp. of America, the fourth-largest U.S. producer of corrugated shipping boxes, has agreed to buy container board-maker Boise Inc. for about $1.27 billion in cash to add capacity in the Pacific Northwest and Europe.

Packaging Corp. will pay $12.55 a share, the companies said Monday in a statement, 26 percent more than Boise’s Sept. 13 closing price. The deal also includes $714 million of Boise’s debt and will close in the fourth quarter, they said.

The takeover will increase Lake Forest, Ill.-based Packaging Corp.’s container board production capacity 42 percent to 3.7 million tons a year, the companies said. Packaging Corp. forecast pretax savings of $105 million within three years of the deal’s completion from cutting transportation costs and other efficiencies.

Boise, based in the eponymous Idaho city, also makes newsprint and office paper and owns mills, production facilities and distribution centers in North America and Europe. The shares surged 26 percent to a record $12.56 in New York. Packaging Corp. advanced 11 percent to $60.43, the highest since the shares were first sold in January 2000.

The combined companies generated $5.5 billion in sales and $879 million in earnings before interest, taxes, depreciation and amortization last year, according to the statement.

Packaging Corp. said that it will refinance Boise’s debt with a $2 billion debt offering, raising the combined company’s total borrowings to $2.5 billion.