Adobe's instructions for high res printing:

The Acrobat Distiller PPD file is included with the Acrobat Distiller 3.0x software and is installed in the Xtras folder in the Adobe Acrobat 3.0x folder (Macintosh) or Acrobat3 > Distillr folder (Windows). This PPD does not write device-specific information in the resulting PostScript file, so you'll still be able to select certain high-end controls, such as custom paper sizes, for oversized jobs. The Acrobat Distiller PPD was originally written to create PDF files for on-screen viewing, so we recommend making the following modifications to ensure consistent, reliable results: 

Change the DefaultColorSpace value from RGB to CMYK 

Change the DefaultResolution value from 600 dpi to 1200 or 2400 dpi (based on your final output device) 

To edit the PPD, perform these steps: 

1. Open the Acrobat Distiller PPD in a text editor and locate these lines of text near the beginning of the file: 
 *% ==== Device Capabilities ===============
 *ColorDevice: True 
 *DefaultColorSpace: RGB 

2. Change the DefaultColorSpace value from RGB to CMYK as noted below:
 *DefaultColorSpace: CMYK 

3. Locate these lines of text further on in the file:
 *% Multiple Resolution support for Distiller 3.0 ==============
 *OpenUI *Resolution: PickOne
 *OrderDependency: 50 AnySetup
 *Resolution
 *DefaultResolution: 600dpi 

4. Change the DefaultResolution value as noted below (or set the value to 1200 dpi):
 *DefaultResolution: 2400dpi

5. Locate these lines of text near the beginning of the file:
 *PCFileName: "ADISTILL.PPD"
 *ShortNickName: "Acrobat Distiller" 

6. Edit the text to read as follows:
 *PCFileName: "CMYKDIST.PPD"
 *ShortNickName: "Acrobat Distiller CMYK" 

7. Save the edited PPD file in text-only (ASCII) format to the same location, using the file name CMYKDIST.PPD so that you can easily distinguish the edited PPD from the original.