[pdftex] controlling a4/letter from tex?

[Karl Berry]

This seems like it is probably a FAQ, but I could not find any Q (or A).

For pdftex, is it possible to control the final page size from within TeX?
Or is it necessary to set page_width and page_height in pdftex.cfg?

Setting \pdfpagewidth and \pdfpageheight made no difference.  (This is a
plain TeX document, namely, the TUG membership form at
http://tug.org/forms/current/memberapp.tex.)

Since texexec has a --mode option to set this, I guess it is possible,
but I could not figure out what texexec and/or ConTeXt is doing as a
result of that option (and it didn't change my output, either).

In any case, if it's not possible to change the page size from within
TeX, I suggest a command line option to allow loading an arbitrary
config file.  This would be more convenient than having to create a
new directory with the necessary pdftex.cfg in it, which is what I
resorted to.

Sorry if such an option is already there, I didn't see it in the --help
output.

This is with pdfTeX (Web2C 7.5.2) 3.141592-1.11a, from TeX Live 2003.

Thanks,
karl