Can I assign price books to contacts, invoices or purchase orders?

Can I assign price books to contacts, invoices or purchase orders?

Hello, 

I recently created several price books in Zoho CRM and assigned products to each price book with special prices.

But I do not know how to assign the price books to contacts, invoices or purchase orders? 

The best way would be to assign a price to a contact. So if i.e. a dealer has special price conditions the discount would be used in every invoice or purchase order. 

Or am I completely wrong how price books work in Zoho CRM? 

Thanks for help, 
M.