While doing some general tests with this post, it appears that this simple command crashes my whole Mathematica session (Mathematica 11.2.0, OSX 10.11.6):
ExportString[Style["hello", FontFamily -> "YuGothic", FontSize -> 12], "PDF"]
It seems only to concern this ("YuGothic") particular OSX font and "PDF" export ...
(Print@{#, ImportString[ ExportString[ Style["ěščřžýáíé", FontFamily -> #, FontSize -> 12], "PDF"], "TextMode" -> "Outlines"][[1, 1]] // Graphics}) & /@ $FontFamilies[[1 ;;]]
doesn't crash FrontEnd v.11.2.0 on Windows 7 x64, so it is seemingly an OS-related problem. $\endgroup$