Shipping is always combined for multiple purchases. You only pay one shipping fee no matter how many paper items you buy.
Please note if there are different shipping fees among the items you buy, the highest fee is charged. If you purchase multiple items a small incremental fee for weight may be added.
The Paypal invoice will not automatically combine the shipping. I will send you an updated invoice with the reduced shipping if you purchase multiple items.
Please feel free to wait to pay if you are bidding (or planning to bid) on multiple items.