[MiKTeX] Letterpaper

[José C. S. <jcs...@fc...>]

Hi all,

If I compile this file with PDFLaTeX (under MiKTeX 2.7):

\documentclass[a4paper]{article}
\begin{document}
The article under review contains a proof of the fact that
$2+2=4$. However, not only the statement is well-known as,
furthermore, to proof is flawed.
\end{document}

I get (not surprisingly) an A4 size document. However, if

    a4paper

is replaced by

   letterpaper

I still get an A4 size document. Why is that?

Best regards,

Jose Carlos Santos