This rejection is caused by a non- PDF document that has been saved or renamed with a .pdf file extension.
you don't see the %pdf-header because that's part of the file's metadata that's contained within the file.
most versions of turbotax don't allow the e-filing of any attachments. rather they must be submitted separately with form 8453. only certain forms are supported by the 8453. if your's is not one of them the entire return will have to be mailed in with the attachments printed out.
