Worked like a charm, after finangling the installation. In case someone else comes upon this thread and decides to use this solution, the current (5/27/2009) instructions don't quite work on 10.5.6. The package file installs correctly, but when opening the Print and Fax Preferences pane, the CUPS-PDF virtual printer option did not appear when trying to create a new printer, even following the "advanced" instructions. So, get into the CUPS configuration directly, bypassing the perfpane. Here's how:

1. Access the CUPS console by opening this url in a browser: http://127.0.0.1:631/
2. Click the Administration tab and the Add Printer button
3. In the Add New Printer window, give it a descriptive name and click on Continue (other fields can be blank)
4. In the Device for <printername> window, choose the CUPS-PDF (Virtual PDF Printer) item from the drop menu, click Continue
5. Select Generic for Make, click Continue
6. Select Generic Postscript Printer on Model, click Add Printer. The browser will open an authorization dialog, use your Admin-enabled username and login password.
7. At this point you have the printer created but not with the correct profile for color printing. You can quit the browser.
8. Open Print and Fax Preferences in System Preferences and select your newly created printer
9. Click on Options & Supplies and click on the Driver tab
10. Choose the Generic postscript color printer option, click Ok. Now you have full color support.