[OS X TeX] \includegraphics question

[brian at pongonova.net]

I'm using information in this FAQ
(http://www.cds.caltech.edu/info/cds/MacTeX/FAQgraphics) to include
some PDFs.  If I just place a PDF (websurvey_pg1.pdf) in the
directory, with the following directive:

\includegraphics[width=6.3in, height=8.7in]{websurvey_pg1}

I get the following error when running latex:

dissertation.tex|1055 error| File `websurvey_pg1' not found.

OK, so I create an EPS file and recompile:

$ pdftops -eps websurvey_pg1.pdf

and a beautifully rendered page with my PDF embedded is produced.
Thinking that I no longer need the PDF file (remember, I just
generated an EPS file), I delete the PDF.  Upon recompiling, I receive
this thoughtful message:

Error: pdflatex (file websurvey_pg1.pdf): cannot find image file
 ==> Fatal error occurred, the output PDF file is not finished!

Hmm...so I guess it needs *both* files!  Indeed, my guess is correct:
Upon restoring the *original* PDF file (alongside the EPS file), all
works as expected.

So, what gives?  Why is not the PDF *or* the EPS alone sufficient for
latex to do its thing?  It's more of an annoyance than anything,
because I end up having to generate an EPS file for every PDF I want
to include.

  --Brian