Reply To: scaling a document up

I don't know, I haven't been scripting specifically for Cs5. But the ref says it's an array, not a single value, so you could try

pasteboardMargins = [ “6in”, “6in”, “6in”, 6in ];

The ref does not mention how it works; I would guess it adds these amounts all around. If you cannot get it to work, look at what is reported for the values are in your current document:

alert (“Pasteboard is :”+app.activeDocument.pasteboardPreferences.pasteboardMargins.join(“, “)+” big”);