lpr -o scaling=50 - works sometimes

[Nraygun]

I've used the command in the subject on a PostScript file generated by using Adobe Reader on a PDF in Linux.
In Ubuntu, the command properly prints a 50 scaled version of the PDF using a generic PostScript driver.
In OS X and OpenSuse it doesn't work.
I also noticed that when I do a lpoptions, sometimes it shows the scaling option and sometimes it doesn't. I was able to make it appear by changing the default scaling in the driver to something other than 100%.

Can anyone shed any light on what makes scaling work properly on a PostScript job?