In compliance with government regulations, exit row seats are only assigned to physically able passengers over the age of 15 who are capable of understanding cabin crew instructions and assisting other passengers during an emergency evacuation, and these seats cannot be reserved in advance.
Even after a paper boarding pass has been issued, you can still issue and use an online boarding pass through the website or mobile app. (This service is limited to eligible passengers and at airports where online boarding passes are accepted.) However, for flights departing from Korea, if you reissue an online boarding pass, the original paper boarding pass will be voided. Please be sure to board using the most recently issued boarding pass.