Sorry. You cannot attach pdf's to an e-filed return. You need to enter the W-2's as income on the 1040X and e-file it. If the IRS wants copies they will request them by sending you a letter. Your employer sent copies to the IRS---so the amounts you enter need to match the W-2's. If, however, you are mailing in the amended return, then you must attach paper copies of the new W-2's that were not on your original tax return.