The Subversion Id keyword allows you to include useful information about the repository status of a file into that file. Subversion properties and specifically the svn:keyword Id property are explained in the subversion book

A package has been created that allows Subversion keyword information flexibly in your LaTeX document. Once the package is installed using it is very simple. First ensure that the Id keyword is activated for the file in question:

$ svn propset svn:keywords "Id" foo.tex

(see also various_tips_tricks). Then include the following lines:

\usepackage{svninfo}
\svnInfo $Id$

The $Id$ line will be expanded by subversion the next time you check-in or update foo.tex

The Id information can then be acessed by using the commands of the svninfo package. For example

\svnId

will give you all of the Id information. Each element: filename, date, revision number, user are also available separately; see the documentation of the svninfo package for details.