By default, Path Finder will hide Blotter. The reason for this is that 'Path Finders Desktop' will display on top of Blotter and hide it. There are two ways you can get Path Finder to work with Blotter.
Disable Path Finder Desktop
You can use Blotter and Path Finder simultaneously if you disable 'Path Finder Desktop'. To do so, Go to Preferences in Path Finder and select "Hide Path Finder Desktop.'
Reconfigure Path Finder's behavior
If you still want to use Path Finder Desktop, you can. All you need to do is to re-configure its behavior.
Go to the Desktop and go to 'View' -> 'Show View Options' ( or press ⌘J).
Press 'Set Colors' (yes, we know, it sounds strange).
In the new window, select "Use the Finder's desktop window level"
Blotter should now appear on your desktop.