PDForum A Threaded Interface for Collaborative Annotation of PDF Documents

The Portable Document Format (PDF) is currently becoming the standard for digital documents. One of the tasks regularly performed on digital documents is annotating and reviewing annotated documents. In collaborative annotation, the document is a heterogeneous collection of annotations by several persons, which at some level includes annotating previous annotations done by other persons. Primarily, two different mechanisms exist for collaboratively annotating digital documents: the first method is using sticky notes, which are a collection of expandable layered notes drawn over the text using transparency. The second method is packing the annotations in a message-thread interface where they are grouped by the context of the discussion thread. Our hypothesis is that a threaded interface will help users understand and critique collaboratively annotated documents better than layered interface. Our work was based on the Joanna Wolfe’s studies which revealed three essential requirements for supporting effective collaborative annotation, namely, the need to allow authors to categorize annotations by positive or negative content, a means to provide information about annotators including their general position about a particular topic or text, and a mechanism that helps readers sort and filter annotations systematically In this paper, we present PDFORUM, a tool for supporting collaborative annotation of PDF documents as a plug-in for Adobe Acrobat software. The tool provides the ability to annotate (using a type-based classification scheme) as well as rate (positively or negatively) documents contents and previous annotations. Finally the tool provides the ability to preview the annotations using color coding to provide a compilation of all the ratings specified by the annotators. Keywords: Digital documents, annotations, message thread interface, information visualization, PDF