In
pgadmin3,
1)
Goto,
File -> Options
2)
Select 'Logging'
And select the option of your choice.
(Debug option will log everything)
Log location: ~/pgadmin.log
In pgAdmin4,
You need to change the logging configuration using "config_local.py" file,
Add below config option in "config_local.py"
FILE_LOG_LEVEL = logging.DEBUG
Log location: ~/.pgadmin/pgadmin4.log
Please note that log file is created with local user permissions so user can temper the log file.