Check out
this article that goes in-depth into the scarcity of paper and the tight market for all kinds of paper in the commercial printing industry. Most printers are keeping a watchful eye on the marketplace and that makes them uneasy sometimes. Some say it's not so bad, others are having difficulty especially with roll stock for transactional work. And paper mills are converting to other types of stock that sell better and faster. One way to combat this is scheduling your paper buys well in advance if possible. The article is a long read but well worth it if you're concerned about the problem with paper.