Packaging Corporation of America announced that it has entered into a definitive agreement to acquire substantially all of the assets of Columbus Container, Inc., an independent corrugated products producer, in a cash-free, debt-free transaction for a cash purchase price of $100 million.   Under the terms of the agreement, PCA will acquire a full-line corrugated products facility located in Columbus, IN, five warehousing facilities and other related operations located in Indiana and Illinois. ...