We have a receiving department that orders and tracks all of our paper (as well as other supplies). Some clients provide their own stock, but we mostly order from a select group of suppliers. When the stock arrives, it is labeled for the intended job. Most of our inventory is JIT inventory so it usually arrives the day before or the exact day it is to go on press. We do however, keep some common weights and finishes in permanent inventory to deal with rush jobs or stuff that gets printed often (business cards, trifolds, letterhead, etc.)