New version of pgAdmin 4 is based on QT5. When you install pgAdmin 4 on Windows computer with a high-density display you may see that letters are too small.
Solution is to send one parameter to QT engine. It will handle DPI in different way.
Open PowerShell and go to directory with pgAdmin. Then launch application with parameter:
cd "c:\Program Files\PostgreSQL\9.6\pgAdmin 4\bin" .\pgAdmin4.exe -platform windows:dpiawareness=0
You can persist the configuration by creating qt.conf. Start PowerShell as Administrator. Go to directory with pgAdmin and create the file:
cd "c:\Program Files\PostgreSQL\9.6\pgAdmin 4\bin" notepad qt.conf
Write there following content:
[Platforms] WindowsArguments = dpiawareness=0
Save the file and start pgAdmin 4 and enjoy new font size.