[tex-k] pdflatex question

[Karl Berry]

    a unix system that insists on creating a4 paper. I cannot find a
    pdflatex.cfg file.

With teTeX 3.0:
texconfig paper letter

I believe that will also rebuild the .fmt files, which is needed in 3.0.

With earlier versions, you have to configure programs separately:
texconfig pdftex paper letter
texconfig dvips paper letter
etc.

Hope this helps (if the other answers didn't already solve it),
Karl