PDFs do have their benefits. They also have some downsides. They are a nightmare for version control, they can’t be edited easily, once downloaded they can be shared without permission, they are difficult to read on mobile devices due to the lack of responsive design, analytics and user engagement metrics are limited, the list goes on.
For these reasons, other technologies started to pop up in the late 1990s and even newer technology is popping up today. One of the technologies that popped up in the late 90s is the flipbook.