The macOS Default application for opening PDF files is Preview. The Preview App is very capable. However, I prefer to open my PDF files with Readdle Software’s PDF Expert. It occurred to me that many people that have Macs (especially new users) may wish to assign a different App besides Preview to interact with PDF documents. This article explains just how to do that. By the way, you can apply what you learn in this article to change the Default App for opening all kinds of different document types.