I want to add my wife to my property deed, do I have to rewrite the deed or can I just file an affidavit?

You will have to sign a new deed to her.  Preparing a deed would probably be easier and cheaper than preparing an affidavit even if it could be done by affidavit.  Unless there are tax or other reasons to not do so, I recommend that you instruct your attorney to prepare the deed so that you and your wife will each own a 1/2 interest in the property but that, upon the death of either of you, the full title would automatically vest in the survivor.