There is a 32 page Congressional report on Pakistan's nuclear weapons.
Dr. Samar Mubarakmand, a scientist closely involved with the country’s nuclear weapons program, stated in a 2016 interview that only China, France, Russia, and the United States have more nuclear weapons than Pakistan. According to one unofficial estimate, Pakistan has produced approximately 3,000 kilograms of weapons-grade HEU and approximately 200 kilograms of plutonium for nuclear weapons. Islamabad continues to produce both HEU and plutonium for nuclear weapons and is developing and deploying a variety of weapons. A 2014 press report citing Dr. Mubarakmand states that “Pakistan has over 15 types of nuclear weapons, from large weapons that can be carried on fighter jets to small ones ballistic missiles, and even smaller warheads for cruise missiles and tactical nuclear weapons.”
Pakistan’s HEU-based nuclear warheads use an implosion design with a solid core of approximately 15-20 kilograms of HEU.48 Pakistan has also produced plutonium-based warheads, which likely contain approximately 4-6 kilograms of plutonium, according to one expert estimate. Pakistan has reportedly addressed issues of survivability through pursuing a second strike capability, possibly building hard and deeply buried storage and launch facilities, deploying road-mobile missiles, deploying air defenses around strategic sites, and utilizing concealment measures.