I know there are certain posts regarding this topic, but my personal experience was a bit different , so here is how to obtain KSA license from UAE license or any GCC country.
There are two options:
1). keep your UAE license and get KSA license, for which you have to do everything like a newbie, e.g, computer test n written test etc etc,
2). they will take UAE license from you and give you KSA license after some small formalities.
As i choose the option 2, so here what you have to do or need:
1. copy of your iqama & UAE license
2. one passport size photo (4 X 6 cm) (better to keep 4 with you)
3.letter from sponsor
4. copy of passport
5.blood group report.
6. A form in Arabic (which a guy outside fill it for 10 SAR, with file)
7. One can get the same form free from inside n fill it, if you knw arabic.
after getting your file ready, go to building no.2 (in Dallah driving school -near exit 4).
go to left side with counter name Eye test, no eye test was taken , he just sign n stamp your form, n tell you to go to building 4.(do tell him you have a UAE license).
At building 4, they will take a small road test from you, 50m circle of a round about,(not tough, even if you stop your car at start, still they pass you).
Then again come to building no. 2 go to license checking section, again he sign n stamp n tell you to go to building 1.
At building 1 after taking sign from "CAPTAIN" u give them your file and they will give you , your license in half an hour.
try to pay the 400 SAR driving license charges via internet/mobile banking, as its easy and save you 50 SAR.
Hope it helps.