  Adobe's Portable Document Format (PDF) is a popular way of distributing
view-only documents with a rich visual markup. This presents a challenge to NLP
practitioners who wish to use the information contained within PDF documents
for training models or data analysis, because annotating these documents is
difficult. In this paper, we present PDF Annotation with Labels and Structure
(PAWLS), a new annotation tool designed specifically for the PDF document
format. PAWLS is particularly suited for mixed-mode annotation and scenarios in
which annotators require extended context to annotate accurately. PAWLS
supports span-based textual annotation, N-ary relations and freeform,
non-textual bounding boxes, all of which can be exported in convenient formats
for training multi-modal machine learning models. A read-only PAWLS server is
available at https://pawls.apps.allenai.org/ and the source code is available
at https://github.com/allenai/pawls.
