The page size of my document is 6 x 9. When I "Print > Save as Postscript..." the resulting PS document comes out as US Letter Size. I can't find a way to specify the output size for PS printing/saving. Any suggestions?
Interesting, not perhaps for you, but from the point of view of technical writing. Why? Because of the difference in the printing philosophy for Mac OS (PS and raster) versus Mac OS X (PDF and raster).
In principle, in a PostScript process you have to have the device parameters as defined in the PDD PostScript Printer Definition at the point when the PostScript program is written.
The device parameters define such things as the format facilities of the device, the paper feed facilities of the device, and the colourant models of the device.
In a PDF process you do not have to have the device parameters at the point when the PDF is written, in fact you try to avoid this by writing the page description at a higher level of abstraction.
Things permitted in PostScript and EPS are prohibited in PDF, including such things as programmed screenings (possible in Photoshop) and transfer curves (possible in Photoshop).
Moreover, in so far as possible you should never (meaning never, never) write out PostScript to disk in order to convert that into PDF. Adobe Acrobat Distiller has been a dead product for a decade because PostScript does not support the intelligent profile model of the International Colour Consortium, the intelligent font model of the Unicode Consortium, or indeed transparency.
/hh