I use emacs23 in my laptop (Ubuntu). I would like to obtain a PDF file with pdflatex. But I don't know how to do. I am a beginner in using emacs23.
If you use AUCTeX set the variable
to your ~/.emacs
When the variable is set to true
AUCTeX is packaged for Ubuntu. To install it do
Asking such questions is not a promising approach to learn how to use Emacs. You need to read a manual or at least a tutorial about Emacs -- there are many on the web, probably in your language -- and as well about the Emacs extension AUCTeX. Emacs is much more difficult to use than e.g. Kile, but after you've spent some days on learning how to use it, you'll be better off.
I do not recommend to start learning LaTeX and Emacs at the same time.
EDIT: Andrew Stacey convinced me to add links for readers who take a start with Emacs and AUCTeX in English.
The Tutorial provided by Emacs is excellent, Emacs asks you to do it when started for the first time. However, here is a link: http://www.gnu.org/s/emacs/tour/
As a second step, install and learn how to use AUCTeX, see here: http://www.gnu.org/s/auctex/manual/auctex.html
And no, there is no easy way to learn it. You have to invest some time. But even me -- a busy lawyer in Germany in the forties -- managed to comprehend it. Hey, Emacs + AUCTeX and LaTeX is stable and reliable.