Here's an example of how I learned to control line spacing in lists for PDF documents.

Basically, the reason I use this is that I am writing some requirements specifications for software applications, and by default the line spacing for lists and enumerations is too large. It appears that the items are double-spaced, and I really want them to be single-spaced. Like everything else with LaTeX right now, I won't say that this is a perfect solution, but it does work very well.

Here is the code I use to set up the single spacing:

%
% this makes list spacing much better.
%
\newenvironment{my_enumerate}{
\begin{enumerate}
  \setlength{\itemsep}{1pt}
  \setlength{\parskip}{0pt}
  \setlength{\parsep}{0pt}}{\end{enumerate}
}

What I do is insert this code somewhere at the top of the document, before I need to create any enumerations. Then, later in the document, when I do want to create an enumeration, instead of using the enumerate tag, I use the my_enumerate tag defined here. The results are exactly what I want - single-spaced enumerations.