I do not believe so.
Sign up for Interfolio, print out the cover sheet, stamp and label an envelope - give to your writer. All they will need to do is print and sign their letter, attach the form, stuff it in the envelope, and then put in outgoing mail.
Alternatively, they could upload it online to Interfolio, but it is slightly more confusing for the writer if they are technically challenged.
You can upload these letters on your own, but Interfolio will call them "Documents" and not "Confidential LORs."