Can I include an insert in my mailing?

What kind of inserts can I include in my mailing? How do I upload an insert?

We can print and add a one-page 8-½ x 11 b&w letter or press release to a book, one insert per book, for $.15 each.

The insert must be uploaded through Stacks with the drop ship list Excel file.

We cannot do inserts for drop shipments of multiple titles: all customers must enter in a separate bulk ship order for each title.