The title section of my LaTeX documents usually look like
\\title{Title} \\author{Me} %\\date{} %// Today\'s date will appear when this is commented out. \
Simple manual method:
Create a file called (say) version.tex:
version.tex
\providecommand{\versionnumber}{3.0.1}
Where you need to use it:
\input{version} \title{Title\\\normalsize Version \versionnumber}
\input{version}
\title{Title\\\normalsize Version \versionnumber}
This will give you a single common place in your project or projects to update the version manually.