[OS X TeX] PDF background (Snow Leopard/Preview)

[John Maindonald]

When after installing Snow Leopard, I opened several
existing 1-page PDFs in Preview,I found the text obscured
by a black and white checkerboard shading.  An immediate
solution was to use some different pdf viewer (PDFClerk Pro
or Adobe, version 5 actually which is what is on my machine!)
to view the file.  A certain amount of searching revealed that
I needed to turn off

View | "Show Document Background"

For most of my pdf files (all created using pdflatex), I am
not offered the option of seeing the background.  The
following is an instance of LaTeX source that will create
(on my system) a pdf where I am offered this possibility,
thus getting the checkerboard.

   %&LaTeX
   \documentclass[a4paper]{article}
   \begin{document}
   \thispagestyle{empty}

   \textbf{\LARGE An Introduction}

   \end{document}

Why do such documents have a background?  And why do
most of my much longer documents, with a much richer
preamble, not have a background?

I've no idea whether the checkerboard background was on
offer under Leopard.  If it was, it never impinged on my
consciousness.

John Maindonald             email: john.maindonald at anu.edu.au
phone : +61 2 (6125)3473    fax  : +61 2(6125)5549
Centre for Mathematics & Its Applications, Room 1194,
John Dedman Mathematical Sciences Building (Building 27)
Australian National University, Canberra ACT 0200.