I am sharing my personal experience. I already had my home country license and went through following process in Riyadh.
Driving license
Photocopy of:
Iqama
Passport
Your home country license e.g. Pakistani License
4 Photos
Attach Arabic form..SR 35
Attach Arabic translation of PK license.. SR. 50
Blood test SR. 50
Eye test SR. 50
Then reception no. 1. Get stamped and goto yard to test drive. Come back and at reception 2, pay SR. 100 and get a date for theory And road test same day test after 2 weeks approx.
At the test day, there will be a theory class in Arabic last part in English in room#2. Pay attention in class. You will be given clear hints how to choose correct answers.
After an hour class go to room #4 sit and wait for your name to be called.
When called, go to room#3 for test.
Once pass, go to ground for driving test. Sit and wait in lounge until your name is called. Last driving test.
Once passed. Go to reception#1 area sit in front of director school office where your name will be called to collect your green file. Go to opposite hall collect a token and go to main gate and pay for license in room #2 and come back where you took the token. By then your number should come. Give your green file and sit. Wait till your name is called. This time you go to window and collect your license. I got mine for ten years!
P.S. My sponsor is in Khobar but I did all process in Riyadh. So it's possible and no big deal. Also you do not need any sponsor letter to obtain Saudi drivers license.