If this doesn't work, please provide the following:
[moderator: moved post to new discussion topic and edited title for clarity]
This is one of Apple's exciting new features in Safari 14. They are ahead of the curve. While Flash Player is going away for everyone else at the end of this year, Apple have given Mac users an early experience of this. Yes, by design, Safari 14 blocks Flash Player completely. For a couple of months you could use another browser, like Chrome, then it's all gone. BUT, that said, your link is a PDF. It does not need Flash Player at all, and will not be going away at the end of 2020. What happens when you try to view it?