Yes you. However, you will need to first determine what you want to use as stocking unit. The stocking unit is like that base unit of the product. You will do you inventory valuation based on the stocking unit. You will be building your BOM based on your stocking unit. Even though the system allows multiple UOM for the same product, but in many aspect, it's always been converted back to stocking unit behind the scene. And therefore, once it's been determined, it's strongly recommended not to change it after you have transactions against the product.. 

Once you determined your stocking unit, you can have various UOM related to the product. You can have default purchasing UOMs based on the suppliers, or default sales UOM based on the customers. You can also setup different "packing" UOMs, such as box, case or crates, and you can choose to manage your warehouse based on these packing UOM. For example, if you choose to manage packing UOM in your inventory, you will be able to see you have 4 crates, 3 cases and 1 box of sugar in your inventory. Since the stocking UOM is the base UOM, the system will require you to setup the conversion rate between the various UOMs and the Stocking UOM. 

Thanks Michael. I see that I can put in by default up to 4 packing UOM for each product. I see a KB article explaining how to extend this number. Do you know of any negative impact on doing this?

If you are planning on managing your inventory with pack unit, you need to understand the implication. You need to understand that the pack unit will be part of the stock line. The system keeps track the inventory in cases and inventory in boxes separately. You are required to enter a stock change transaction if you which to change the UOM, for example, breaking a case into 6 boxes. In your physical count, you will also need to count them separately. Instead of counting the total of 400 lbs, you will need to enter the inventory qty that are in cases, qty that are in boxes, and qty in loose lbs separately. It's a very neatly control system, but could get overwhelming if you manage too many Packing UOM's in your inventory. 

Thanks Michael.

Actually for this situation, we are not using products for inventory at all. The client does not manage inventory themselves and simply want to setup products so they can be added to Purchase Request/Order on a recurring basis. Based on this, is it reasonable to expand the number of pack unit or should I keep it to the default number?

I see. As the it mentioned in support's KB, this is not the intended design for the pack unit. You can attempt to increase it as in KB, but you will need to make sure you tested all functions that the product and pack unit are used just to be sure. I would suggest you to minimize the number of Pack unit line to increase. There are some hard code limit in some functions. However, since the products are not stock managed, I suspect the impact should be relatively minimum.