PSPDFKit is a framework for iOS, macOS, Android and Web that deals with everything related to PDF. It's a large framework and we expose a lot of API so many aspects can be customized. The API can be intimidating at first but you really only need the basics to get started.
PSPDFKit for macOS is the youngest child in our PSPDF family. It is based on the exact same core that powers our iOS framework — sans views.
Note: We are currently in the process of porting and unifying the iOS guides with the macOS version. Meanwhile we encourage you to also take a look at our iOS guides, most of which apply to the macOS version as-is.