Aaah, trial versions on the App Store :( I'm still not sure what would be the best way to implement a demo version for an App Store only app - I loathe the "Free with IAP" model. If you want to test if your scanner works with PDFScanner, try to use it with the Image Capture application that comes with macOS. It uses the same library as PDFScanner to talk to the scanner, so if your scanner works there, it will also work in PDFScanner.