Some PDF viewers will offer a limited set of rescale capability. Foxit Reader (a free PDF program with a great feature set) offers the following:
A 66.7% print of a 1:33 model results in a 1:49 scale. Very close to 1:48 and for most people close enough. I did just check and Adobe Acrobat Reader does not have this scaled print capability. I also checked my printer settings as indicated in SCEtoAUX's post and found that I also have the scale print option there. Never noticed it before. I also normally rescale in a graphics editor so I can use yet another rescale method - increasing the print resolution so as not to lose any digital data in the rescale. It also allows me to rearrange parts to fit on less paper.
Edit: Just noticed the scaling list under the preview of the image. You can type there and add a custom scale. So there you have it folks, download and install Foxit Reader from http://www.foxitsoftware.com/pdf/reader/
and you can scale very easily.