Originally Posted by tompe
Not in 2.1 at least: "The page context has no notion of fonts, so 'em' and 'ex' units are not allowed. ". Since they are not alllowed it is unspecified what happens if they are used. It would be correct to turn off the reader when you see an em in a @page specification.
thanks, I hadn't thought of the @page wouldn't know about fonts although I would expect it to have a notion of the default font size, perhaps not.