Pardon me for living? Means what? Thanks in advance!
Yes, it literally means "I'm sorry I am alive", "I apologize for surviving", or something similar. It's an expression of self-hatred. As you can probably imagine, someone who is severely depressed may say this seriously.
In addition, it's often used fairly casually/jokingly/slangily to express one's sense of embarrassment or inferiority. On SNS, you will mainly find this usage, and people usually don't take this expression too literally. You may regard this as a recurring joke. For example:
there were so many good-looking guys at the party. i thought "i'm sorry i am alive" lol