Requirements for applying Visa for wife:-
1, copy of personal id or passport of the resident husband
2, Letter from husband's employer citing profession and salary
3, copy of attested marriage & child birth certificate
4, copy of wife valid passport
5,  Bank Statements (stamped) for minimum of 6 months ( I'm not sure)
6, Residential tenancy contract
For attestation & translation please contact sheen services as they are the best in Qatar who is very flexible, reliable with competitive price.http://sheenservices.com/contact-us.html