I now aim to show the percentage sign also when you run, for example, the command
man emacs
If you run it, you get \'byte 3300\' for instan
On Linux I just go to the end of the man page with Shift+G then return to the beginning with g. (Or you can return to your previous position with '').
Less then has enough information to display the percentage of how far through the file you are. (You might need to type -M to get the long prompt.)
It's a bit of a hack but only two key presses. Not sure if this works on OS/X.