In PTPublisher 4.0 we were forced to remove Discover disc design software because it was a 32-bit application. Mac OS 10.15 Catalina only supports 64-bit software so this change was necessary to make PTPublisher compatible. However, you will still be able to print JPG, TIFF and BMP files. No Discover Files will work.
You will need to export any of the designs you use as Jpeg files. If you have already updated to Catalina you cannot open your discover files in Discover because it will not run on 10.15. However, Belight makes an inexpensive easy to use a software called Swift Publisher which allows you to create disc designs or open Discover files and export them as Jpeg files. You will then be able to use them in the new version of PTPublisher.
If you need to design new disc images or redesign your existing images you can also use any design program such as Adobe Illustrator. Create a 4.72” (120mm) square with a circular clipping mask as the template for your design. Once your design is complete, export the file as a 300 dpi Jpeg.