NEW YORK — When shoppers walk into JAM Paper, they can choose from hundreds of holiday bows, rolls of wrapping paper and gift bags, in addition to thousands of everyday stationery items. Yet the store will account for just 2 percent of the company's business this year. JAM Paper now gets so much of its revenue online that the company has scaled back from five stores to a single Manhattan location, owner Andrew Jacobs says. "The second we launched the website in 2007, we became national,"...