VBA Page Setup when using ExportAsPdf

My workbook is on a network location and is available for anyone to use it. The purpose is to export a formatted report as a PDF.

ws.ExportAsFixedFormat _
Type:=xlTypePDF, _

Problem is that one user has his PC connected to a Label printer, so default page size is tiny and it throws all sorts of issues with the PDF.
I'm not sure where the page size comes from - whether it's the driver or whatever.

How do I set the page properties so I get a good print/PDF every time, but not disturbing the users settings?

thanks
Guy