SDN Members don't see this ad. (About Ads) I recently got an email from BU saying my app was on hold because one of my letters was not "signed or on letterhead." That letter and two others were all uploaded via pdf through AMCAS' letter writer website. Is there any way I can instruct my lor writer to sign or use letterhead through this method, or does he have to mail it in? Has this happened to anyone else? Is it going to happen at every school now ?