Variable Page Documents
When you have a PDF document that contains letters for multiple people, but the page numbers vary (for example, Susan gets 1 page, Willie gets 4, and John gets 2) we do indeed have a solution for you. However, that is something we will need to assist with as it's an advanced option. The main requirement is that the addresses for everyone must exist in the same location throughout the master PDF file.
If this sounds like your situation, send us an email! We'd love to learn more about your project and help you send out your mail.