For example, if the project manager instructs purchase of items like special types of printer papers, where is this covered in SCC?
It depends who is consuming it and whether it is under NEC3 or 4. I only have NEC3 to hand, but think the location is pretty similar in NEC4.
Under NEC3 Engineering & Construction Contract, if the PM has ordered it for their own offices then it is People 43(i) of the full SCC and paid at cost + Fee. If it is for the Contractor - although I don’t know why the PM would be ordering it for the Contractor - it would be consumable Equipment as perEquipment 25.