The PK is the original version from which all variants were derived. It can be distinguished from the later PKM by its fluted barrel and longer flash hider.

The PKM is an improved version of the original PK that entered service in 1969. It is a lightened version that is made out of stamped metal and uses a non-fluted barrel and shorter muzzle brake. The M in PKM stands for Modernizirovannyi, which is Russian for modernized.

The PKS is a PK that has been modified for use on a tripod. It has a mounting bracket under the gas piston just in front of the receiver. The S in PKS stands for Stankovyi, which is Russian for mounted. The PKMS features the same lighter barrel as the PKM and is normally fitted on the much lighter Stepanov tripod.

The PKB is a PK that has been adapted for use as a pintle mounted weapon. A swivel has been attached to the middle of the weapon. The PKMB features the same lighter barrel as used on the PKM. Some PKB's used on helicopters are fitted with spade grips instead of a pistol grip and shoulder stock.

The PKT is a highly modified PK for use as a coaxial weapon. The PKT is solenoid fired and lacks the pistol grip and shoulder stock. It features a much thicker and longer barrel to mimic the ballistics of the SGMT, therefore avoiding the need to change vehicle optics to match a new trajectory. The improved PKMT has a different type of flash hider.

The Type 80 is the Chinese production version of the PKM. It is generally similar to the original PKM but differs in minute details. The Type 80 is fitted with a tripod mount for a lightweight tripod that can also be converted for anti-aircraft use. The CF06 is marketed as an export version that fires the 7.62x51mm NATO round. The Type 80 was not the first variant of the PK to be produced in China. Decades earlier the Type 59T was already in production. The Type 59T is a direct copy of the PKT. The newer Type 86 is a PKT derivative of the Type 80 and currently is in production.

The M84 is the Yugoslav version of the PK that remains in production in Serbia. The design is derived of the original PK, but differs in various areas. The M84 has a solid wooden stock and a non-fluted barrel. It is also fitted with a tripod and night sight mount, removing the need for special versions. The M86 is a coaxial model of the M84 with a much heavier barrel and solenoid trigger mechanism.