Not sure where should I send a feedback about it, but coming from the link on backerkit I got here (to itch.io) only to find this:
After navigating back to the project page I was able to download the pdf file with no issue, but I'm afraid it won't work with the updates later on. (Edit: The Download button on the top also leads back to the empy page, it's the download button under Download demo that works.)