A friend recently asked what happened to the ability to export color separations from Adobe InDesign CS5 to a PDF using custom page sizes. I’ve never heard of or had the need to do this, so I was of little help. But for whatever reason, I was able to do it because I still had the generic Postscript PPD installed. The only thing I could think of was that I still had CS4 installed on my Mac, and the ability to do it remained in CS5 because of that.
In any case, my friend discovered the work around, and shared with me where he found it. Russell Viers offers the solution, that requires little more than a quick PPD download and install. Again, I’m not sure why you would want to do this because your printer generally handles this in-RIP at their printing facility. You really need to know what you’re doing when you enter the settings.