I worked at Adobe for 9 years and helped develop PressReady. You may still be able to order it directly from Adobe, or from HP, but make sure you get the specific version that was made for your printer.
That said, if you simply get Acrobat and print your documents to PDF, then print the PDF to your printer using Acrobat or Reader, you'll get pretty much the exact same results.
Which is a big reason why PressReady and similar PostScript Interpreter software pretty much dried up and disappeared.
In the interests of 68K compatibility, even Acrobat 3.0.x was pretty good at this.