PDFAnno: a Web-based Linguistic Annotation Tool for PDF Documents

We present PDFAnno, a web-based linguistic annotation tool for PDF documents. PDF has become widespread standard for various types of publications, however, current tools for linguistic annotation mostly focus on plain-text documents. PDFAnno offers functions for various types of linguistic annotations directly on PDF, including named entity, dependency relation, and coreference chain. Furthermore, for multi-user support, it allows simultaneous visualization of multi-user’s annotations on the single PDF, which is useful for checking inter-annotator agreement and resolving annotation conflicts. PDFAnno is freely available under open-source license at https://github.com/paperai/pdfanno.