How do you set overprint in PS CS3?

I think the image/document must be in greyscale first - this is from the PS CS3 help

Choose Image > Mode > Duotone. Click Overprint Colors. The Overprint Colors dialog box shows how the combined inks will look when printed. Click the color swatch of the ink combination that you want to adjust. Select the desired color in the color picker, and click OK. Repeat steps 3 and 4 until you are satisfied with the ink combination. Then click OK.

Napalm, did you get this sorted out?

to the best of my knowledge, I would suggest saving as a Photoshop PDF and using the print dialog from Acrobat... then again, I have Acrobat Pro, and don't know that the print dialog from Reader will get you what you need

the other response would have been to place the Photoshop document in InDesign for more-sophisticated print requirements

I got it sorted thanks. I had to change all the text layers to multiply, and re-export everything

that sounds like one of the effects or workarounds I had read about glad to hear it worked for your purposes