First, I'm sorry if this is the wrong place to ask this question.
As in the title, does anyone knows the shipping fees to Italy? I always bought the PDFs, but with the sale I figured that I afford ordering something in bulk.
Also, let's say that I order some available products and one in backorder: will I have to pay shipping fees twice, or I can make it so everything is shipped together when the backorder is available?
I'm not totally sure what you mean by fees. If you just mean the cost Paizo charges you for shipping, you can put stuff in your cart and start the checkout process to see the shipping cost before you actually submit your order.
If you means customs fees, that I have no idea.
And backordered items will ship separately from in stock items. I'm not sure if there is anything Paizo can do about that.