Generally: No.

Media mail regulations are very strict: only media (books, CDs, DVDs, VHS tapes) and an invoice (page 2 of the PBS wrapper qualifies as an invoice) are allowed to be sent using Media Mail rate.  No advertising, commercial solicitation, political materials, religious tracts, non-Media items, letters, cards are allowed.

PaperBackSwap rules preclude including extraneous materials such as advertising, commercial solicitation, political materials, religious tracts, non-Media items, letters or cards. Including inappropriate materials with your PaperBackSwap package (whether sent Media Mail or First Class Mail or any other postal rate) will jeopardize your membership and can result in termination, even after a first offense.

More about the Postal Regulations.

• Media Mail is subject to postal inspection
• If your package is found to be in violation of Media Mail regulations:
  • Your package may be returned to you
  • Your package may be delivered to the requestor postage-due
  • Your package may be destroyed.

What is Allowed in a package sent using Media Mail rate:

• Media, as described above
• A note with a simple accompanying message,
  • such as "Happy Birthday!" or "Hope you enjoy it!"
• An invoice or notification of the shipment
  • The second page of the PBS Wrapper falls into this category.
  • The USPS eligibility guidelines for enclosures and attachments for Media Mail say (we have edited these for relevance; the full regulations are at http://pe.usps.com/text/dmm300/173.htm#wp1060522)

  • 4.0 Attachments and Enclosures

    4.2  Enclosures in Books  (bound into the books)

  • 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..

    4.3 Written Enclosures

  • Markings that have the character of personal correspondence require, with certain exceptions, additional postage at the First-Class Mail prices. The following written additions and enclosures do not require additional First-Class Mail postage:

    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)

    4.4 Invoice (page 2 of the PBS Wrapper qualifies here)

    An invoice, whether it also serves as a bill, may be placed either inside a Media Mail piece or in an envelope marked "Invoice Enclosed" and attached to the outside of the piece if the invoice relates solely to the matter with which it is mailed. The invoice may show this information:

    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.

Related Links:

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?