This cannot be done without custom code. I've done it previously by integrating s2Member and Gravity Forms' User Registration addon functionality which was a major undertaking. However, if you use a mailing list management system that allows sending sequential emails, it might be easier to use that. That is, when the user registers/renews you update the mailing list and use a workflow created there to send out the email with the attachment. Capabilities vary greatly among those services so it would depend on which service you're using.