There are two types of PK symbols - one is given for NP (National points) and second is given for LP (Ladder Points).
Symbols given for NP - they are given for TOP 200 players on each side. They have border around them.
Symbols given for LP - they are given for TOP 200 players on each side. They do not have border around them. Ladder points are reseted every month.
There are 6 types of symbol based on position in rank. If you have any of those symbols, you can get small amount of money as reward (on daily basis) - you can take reward in behind Luferson/El Morad Castle.
In below table you can see, what position in rank you need to get some specific symbol and also reward which you can get.
Actual rank is updated once a day (or maybe twice - I am not sure now) and can be found on official website - National points rank or Ladder points rank.