There are two options to find out how many paper is still in your printer.
GoPhoto - Print Station
When the Print Station is turned on and the app is logged in, you can see the amount of paper that's left in the connected printers. When the app is logged in you are automatically in the 'Dashboard' page of the app. Underneath the Daily statistics you see the printers connected to the Print Station. Underneath 'Prints available' you see the number of sheets that are left in the printer.