This document provides an overview of patron-driven acquisition (PDA) models for libraries. PDA involves adding resources to a collection based on immediate patron need. Common models include request forms, ILL-initiated purchases, and ebook programs that trigger short-term loans or purchases based on usage. PDA is intended to better serve users, save time and money, and build collections more effectively. The presenter recommends libraries pilot test any PDA program and consider goals, stakeholders, and implementation. Next week's discussion will cover PDA in practice and its implications for library collections and roles.