Can I add a Note to a PO?

Yes!

You can add a note to an order from within the Review Order screen. There are two types of notes you can add: Notes Visible to Rep and Vendor, where you can share information with the vendor; and Notes for Self, where you can add notes that will only be visible to you, the Sales Rep.

In addition, there is also a Copy Notes From Account button which you can use to quickly add notes that are associated with the account, such as a UPS or Fedex Account number, etc. You can read about this feature in greater detail here.