Eagle PCBs not printing to scale and the letter F shows it?
I actually found a solution that works even though its a crazy one.

First, I had to reset user preferences. As I am using linux, I had to delete .eaglerc file and restart eagle and reload my board.

Then in the printing settings, I needed to make sure the page limit was set to zero instead of one, and also I had to match up my paper sizes in my printer driver to that in eagle. That way, if the page is too large, the board will span onto two pages instead of shrink itself to fit one page. Luckily I wasted little ink thanks to an installed pdf file generation printer on my computer. I also tested my theory with a real printer and it seems to work (at least for normal paper).