Abstract: The invention relates to a method for delivering secret information to a client as a posted letter. In the method, the information, such as a code, is printed and enclosed into an envelope on which the client's address information is printed. According to the invention, a print carrier (1) is provided for printing the secret code, such as a PIN number (2), and concealed client identification information (3) on a same printing surface; the print carrier is glued and folded to form a closed envelope (4) in such manner that the secret code is enclosed inside the envelope but the identification information remains visible; and the identification information is read and used for printing the client's address information (5) onto the closed envelope.

Abstract: A method for folding and glueing a sheet of paper that contains informations and serves both as a letter and an envelope, wherein the sheet (40) is folded transverse to its parallel lateral edges (41). The lateral edges (41), the end edge (45) of the last folded sheet portion (40a) and the transverse edge (46) are closed by glue joints, and the folded and glued lateral edges (41) and the transverse edge (46) are perforated. The travel direction of the sheet is changed by about 90.degree. after treatment of the lateral edges (41). To make the transverse glue joints tight, transverse glueing of the end edge (45) of the last folded sheet portion (40a) and the transverse edge (46) is performed just before perforation of these parts by opening slightly the sheet portions (40a, 40b, 40c) that are to be glued together and by spraying glue on the slots.