I received an offer from Etihad. What type of document do they need to proof Marital status. And do I need to get my degree certificate attested before i submit it or do they do it once I am in Abu Dhabi?

You don’t need to do anything regarding your degree. A high school diploma/GED/BAC will suffice. Send it in in your home country’s language and they take care of the rest. You don’t need to send any degree as it is not required for the job and it might put it as “over qualified” which will basically get you rejected even at this stage.
You will need marriage certificate if you are married (this one must be translated to English and attested/certified.

Good luck