Several dispersed forum/facebook/github/other posts mention that PCGen is almost unreadable on 4k displays, and I also experience that problem. While JavaFX is a forthcoming fix-all, it isn't yet available on all platforms and older versions would forever be left out in the cold.
There is a workaround that I've tested some, though. The Java command line option -Dsun.java2d.uiScale=200% makes PCGen readable on my display.
I see pcgen.sh will append Java options from the command line, but PCGen doesn't seem to have documentation instructing end users how to scale the UI. Where would such a hot tip belong?
Linux desktop with 4k display. XFCE 4.12.