You can download PfT without charge so you can check it works on your computer and evaluate whether it will meet your needs.
Until you pay for a licence and register your computer (so the computer knows about your licence) PfT will operate in Evaluation mode. Once you pay and register the evaluation restrictions are removed.
In evaluation mode you can select emails and click the PfT button. The Messages (tabs) and Messages (grid) pages will show the details of your selection and the Preview page will show what your output would look like out of evaluation mode. (The preview does not show page breaks and does not include attachments.)
It is only on the Output page that evaluation mode imposes any restrictions. You are allowed to print or create output files on ten occasions. This will enable you to check everything is working as it should.
However, the output will not be as you selected it. It will include the cover page summary and the first message.