How do you open a *.pgerd file and view the database diagram?

I have a *.pgerd file that I want to open an view the database diagram. What free tools can I use? I also have access to IntellJ Ultimate Edition, so if anyone knows of plugins I can use, this would also be helpful. FYI : I used https://app.diagrams.net/ to open the *.pgerd file, and it appears to work (i.e. I can see the database diagram, but it looks poorly formatted). So I'm wondering if there are any better tools out there besides app.diagrams.net ?