From the Overview: "Mailing a greater volume of ballots takes considerable planning. This document seeks to help election officials who are faced with scaling up, no matter what their current baseline is for mailing ballots. The following questions and answers focus primarily on partnerships with your procurement office, designers, envelope and mail ballot print vendors, the US Postal Service (USPS), and mail fulfillment centers. Other resources available to election officials as they navigate this set of changes are provided in the last section."
U.S. Election Assistance Commission: https://www.eac.gov/