[Editor's note: This column has been updated to correct the amount of waste paper exported by the U.S., which is about a third, much of which is bound for China.] Companies can make an enormous difference in the global environment and forest communities by adopting strict purchasing policies. Large international companies such as Unilever, Staples, Marks and Spencer and Kraft have all made commitments to sustainable packaging. Thousands of pulp providers, mills, merchants and printers have earned chain-of-custody certification from the nonprofit Forest Stewardship Council, and many publishers -- most recently Simon & Schuster, Inc. -- have committed to increasing their use of FSC-certified paper. In the past year, Nordstrom, Williams-Sonoma and Limited Brands, the parent