export your photoshop image that contains a spot chanel as a DCS 2.0 with single file and 72dpi composite preview...
use a program called DCS Merger to translate your dcs file into an EPS (drag and drop!!)...import the translated EPS into quark and create a postscript file....distill......you will create a Composite PDF with a working spot color.
visit this link for info on DCS merger:
http://www.thepowerxchange.com/freeh..._975_prd1.html
ps - quark is horrible with dcs files...Indesign will handle the DCS 2.0 and properly create a PDF without any extra hassle!!
pps- i have tested the above method with acrobat 5,6 and quark 4,5,6.