I am not aware of an "adjust to page size" setting in yEd's printing options. Could that be a setting of your printer? In that case, the problem lies with your printer, not with yEd. That said, selecting "Entire Graph" as "Clip Area" and "Automatic" for "Scaling" in yEd's printing options has the desired effect for me (see attached screenshot).
Sorry, if I was not precise in my wordÃng!
...selecting "Entire Graph" as "Clip Area" and "Automatic" for "Scaling" in yEd's printing options...
was exactly what I did, but the page is only covered a quarter of the page.