More about the Postal Regulations.
a. Either one envelope or one addressed postcard may be bound into the pages of a book. If also serving as an order form, the envelope or card may be in addition to the order form permitted by 4.2b..
b. One order form may be bound into the pages of a book. If also serving as an envelope or postcard, the order form may be in addition to the envelope or card permitted by 4.2a..
c. Announcements of books may appear as book pages. These announcements must be incidental and exclusively devoted to books, without extraneous advertising of book-related or other materials or services. Announcements may fully describe the conditions and methods of ordering books and may contain ordering instructions for use with a separate order form. Up to three of these announcements may contain as part of their format a single order form, which may also serve as a postcard. The order forms permitted with these announcements are in addition to, and not in place of, order forms that may be enclosed under 4.2a. or 4.2b..
a. The sender's and the addressee's names, occupations, and addresses, preceded by "From" or "To," and directions for handling. (page 2 of the PBS Wrapper qualifies here)
b. Marks, numbers, names, or letters describing the contents. (page 2 of the PBS Wrapper qualifies here)
c. Words or phrases such as "Do Not Open Until Christmas" and "Happy Birthday, Mother."
d. Instructions and directions for the use of the item mailed. (page 2 of the PBS Wrapper qualifies here)
a. Names and addresses of the sender and addressee.
b. Names and quantities of the articles enclosed, descriptions of each (e.g., price, tax, style, stock number, size, and quality, and, if defective, nature of defects).
c. Order or file number, date of order, date and manner of shipment, shipping weight, postage paid, and initials or name of packer or checker.
Including anything but the ALLOWED materials above in your package is a serious infraction of not only PBS rules, but also Federal law. Including inappropriate materials with your books will jeopardize your membership at PBS.
USPS guidelines on attachments/enclosures for Media Mail
How much does it cost to mail a book?
What materials can be sent by Media Mail postal rate?
Do I have to mail from a post office?
How to Print the PBS Wrapper
Wrapping a Trade Paperback Using the PBS Wrapper
What can be posted for swapping here?