If you have credit card you can buy directly without involving anyone else.
There are two types of sellers at Amazon, one is amazon itself and others are direct sellers. Amazon doesn't ship to Pakistan. However, some seller do ship to Pakistan. It is better to ask the seller if they can ship to Pakistan, before placing the order. Do check their rating before placing any order.
Also not all products are shipped internationally. If by chance you happen to buy anything, make sure it is shipped as gift and total value is less then Rs. 20,000/- It will save you duties and tax as well. You will pay nothing.
If it is marked as gift and value is above Rs.20,000, you will have to pay 17% sales tax.
If it is not marked as gift whatever the value is, you will have to pay duties + 17% tax.
amazon.ca & amazon.co.uk & amazon.de ship internationally but limited products.
check also
amazon.com/international