I did manage to put an A3 size page within the A4 document. It contains a landscape figure. My problem is how to save document in pdf format such that the A3 page appear as it is, and not scale down to an A4 pdf.
I'm using a Mac machine and the native 'save as print' functionality creates a pdf file where the A3 page is saved as an A4 page.
\pdfpagewidth=2\pdfpagewidth
so that the pdf viewer doesn't crop that page to A4 – David Carlisle Apr 25 '13 at 12:45