  PeyeDF is a Portable Document Format (PDF) reader with eye tracking support,
available as free and open source software. It is especially useful to
researchers investigating reading and learning phenomena, as it integrates PDF
reading-related behavioural data with gaze-related data. It is suitable for
short and long-term research and supports multiple eye tracking systems. We
utilised it to conduct an experiment which demonstrated that features obtained
from both gaze and reading data collected in the past can predict reading
comprehension which takes place in the future. PeyeDF also provides an
integrated means for data collection and indexing using the DiMe personal data
storage system. It is designed to collect data in the background without
interfering with the reading experience, behaving like a modern lightweight PDF
reader. Moreover, it supports annotations, tagging and collaborative work. A
modular design allows the application to be easily modified in order to support
additional eye tracking protocols and run controlled experiments. We discuss
the implementation of the software and report on the results of the experiment
which we conducted with it.
