21. The smart pen computing system of claim 19 , wherein the first smart pen further comprises: a processor for processing the handwritten annotations captured by the imaging system and for determining an identifier of the printed document based on information captured by the gesture capture system.
19. A smart pen computing system for annotating a printed document having preexisting content, the smart pen computing system comprising: a first smart pen configured to identify a first copy of the printed document having preexisting content and for capturing first handwritten annotations on the first copy of the printed document, wherein the first copy of the printed document is printed from a digital document having a corresponding digital version of the preexisting content; a second smart pen configured to identify a second copy of the printed document having preexisting content and for capturing second handwritten annotations on the second copy of the printed document, wherein the second copy of the printed document is printed from the digital document having the corresponding digital version of the preexisting content; and a non-transitory computer-readable storage medium storing computer-executable program instructions for: receiving the first handwritten annotations from the first smart pen; detecting a background color of a portion of the printed document having the first captured handwritten annotations; receiving the second handwritten annotations from the second smart pen; merging the first handwritten annotations and the second handwritten annotations to generate a collective set of handwritten annotations; associating the collective set of handwritten annotations with the digital version of the preexisting content; storing the first and second captured handwritten annotations in association with the digital version of the preexisting content as an annotated digital document; detecting a background color of a particular area of the annotated digital document, the particular area having at least a portion of the first captured handwritten annotations; and formatting the portion of the first captured handwritten annotations in the particular area of the annotated digital document to have a color selected based on the detected background color.