An authorization letter for HEC is a legal document which gives permission to a third person to go and attest the degrees and transcripts on your behalf. Through the HEC authority letter, you will transfer your decision making power to someone else for the period of time you want to.
You can type this letter on a simple piece of paper and there is no need to put it on a stamp paper or anything else. Moreover make sure that the signature’s on the HEC authorisation letter match those on your National Identity Card. The date on the letter must not be later than the date on which someone goes to get your documents attested. Make sure that you keep the document as concise as possible and only put the required information.