title: rmarkdown: pandoc: pdflatex not found
body: <p>When I use the render{rmarkdown} to produce pdf file from .Rmd file on my Mac, an error message says</p>
  
  <p><code>pandoc: pdflatex not found. pdflatex is needed for pdf output.
  Error: pandoc document conversion failed</code> </p>
  
  <p>However when I check with </p>
  
  <pre><code>pdflatex -v
  </code></pre>
  
  <p>I got</p>
  
  <pre><code>pdfTeX 3.1415926-2.4-1.40.13 (TeX Live 2012)
  kpathsea version 6.1.0
  Copyright 2012 Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX).
  There is NO warranty.  Redistribution of this software is
  covered by the terms of both the pdfTeX copyright and
  the Lesser GNU General Public License.
  For more information about these matters, see the file
  named COPYING and the pdfTeX source.
  Primary author of pdfTeX: Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX).
  Compiled with libpng 1.5.10; using libpng 1.5.10
  Compiled with zlib 1.2.7; using zlib 1.2.7
  Compiled with xpdf version 3.03
  </code></pre>
  
  <p>The pdflatex is installed in my machine.</p>
  
  <p>Can anyone help to tell how can I tell R where to find the pdflatex?</p>
  
  <p>Many thanks!</p>