>
> Is there a configuration or a recipe to cause these A4 postscript files to
> be automagically rescaled to letter-size during the spooling process?
>
There's a psresize command in the psutils package. I couldn't get good
results when I tried to resize an a0 poster to a1 size to fit the printer,
but maybe a plain document A4->letter is simpler to handle.
Victor