David,

You cannot print the grid from within the program, but there is a workaround:
1 - Create a new layer (Plan --> Add level) and make sure it is the lowest layer (if that is what you need)
2 - Draw long "lines" by placing very long, thin boxes; make sure to place the boxes correctly by editing their coordinates.

To print the plan:
1 - File --> Page setup --> Scale 1:120
2 - Set the page size
3 - Print the plan to your printer (File --> Print), or as a PDF (File --> Print to PDF)

Hans