There are generally two types of tags for linking digital content and paper documents. Marker-based tags and RFIDs employ a modification of the printed document. Content-based solutions remove the physical tag entirely and link using features of the existing printed matter. Chunyuan, Laurent, Gene, Qiong, and I recently published a paper in IEEE Pervasive Computing magazine that explores the two tag types’ use and design trade-offs by comparing our experiences developing and evaluating two systems that use marker-based tagging — DynamInk and PapierCraft — with two systems that utilize content-based tagging — Pacer and ReBoard. In the paper, we situate these four systems in the design space of interactive paper systems and discuss lessons we learned from creating and deploying each technology.