Kerala public service commission (KPSC) give an option for add/update the Aadhaar number in candidates profile (One Time Registration). First of all login with username and password in thulasi.psc.kerala.gov.in and follow the below steps.
How to Add Aadhaar Number in PSC Thulasi Website?
1. Login Thulasi site or Click here
2. Click the image in home page (see below)

3. Next you will see below like page

4. Type the 12 digit Aadhaar number and access code, then click save button. Done !