Non-functional after update – PDF Viewer - Annotation Expert Review

I really like this app for the few weeks I used it, but... After installing the update I can no longer open any PDF file. When I click on one, the screen flashes grey with the message "No Document Set" before kicking me back to the document selector. I tried looking up the error on their support site, but couldn't find anything. Since I couldn't find a support email on their site, I am writing a review in hopes that someone who can fix the problem might see it.
Review by Tsubashi on PDF Viewer - Annotation Expert.