Paper is static but it is also light, flexible, robust, and has high resolution for reading documents in various scenarios. Digital devices will likely never match the flexibility of paper, but come with all of the benefits of computation and networking. Tags provide a simple means of bridging the gap between the two media to get the most out of both. In this paper, we explore the tradeoffs between two different types of tagging technologies – marker-based and content-based – through the lens of four systems we have developed and evaluated at our lab. From our experiences, we extrapolate issues for designers to consider when developing systems that transition between paper and digital content in a variety of different scenarios.