I'm taking it you are using the autopackage download from Xara's web site?

You might want to try the package from Ubuntu's development repository (the name of which I now forget, NOT the 8.04 standard one), which is the same code but built with libgnomeprint instead. I think the paper size list is just the wxWidgets standard list in the autopackage version.

Other than that, can you not just save as a PS file and use ghostview to fix it up?