This folder contains data on text simplification collected from an experimental study with second-language university students. We adopted a pre-test and post-test design, and randomly divided participants into experimental and control group. In the pre-test, participants were given an extract of a corporate report dealing with sustainability and were asked to revise it to make it easier to read for a lay customer. Subsequently, they took part in training. The experimental group received training on both plain language and sustainability, while the control group received training exclusively on the topic of sustainability. In the post-test session (2-3 days after the pre-test), all participants were assigned a second extract of a corporate report dealing with sustainability, and were asked again to make it easier to read for a lay customer by applying what they had learned from their respective training. This design allowed us to examine the impact of plain language training on text simplification (revision) tasks. The texts were in English while the participants were native speakers of other languages (mainly Dutch), so the text simplification took place in their second language. This project (PLanTra) has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 888918. Please see "readme" file for additional information.