You're right that it can be done with TikZ, but it's not necessary to load in the whole of TikZ to get the bits required for this. The part that is needed is pgfpages. You can do a lot of page manipulation with this package, but here's some to get you started:
\documentclass{article}
\usepackage{pgf}
\usepackage{pgfpages}
\pgfpagesdeclarelayout{boxed}
{
\edef\pgfpageoptionborder{0pt}
}
{
\pgfpagesphysicalpageoptions
{%
logical pages=1,%
}
\pgfpageslogicalpageoptions{1}
{
border code=\pgfsetlinewidth{2pt}\pgfstroke,%
border shrink=\pgfpageoptionborder,%
resized width=.95\pgfphysicalwidth,%
resized height=.95\pgfphysicalheight,%
center=\pgfpoint{.5\pgfphysicalwidth}{.5\pgfphysicalheight}%
}%
}
\pgfpagesuselayout{boxed}
\begin{document}
Something simple
\end{document}
Of course, if you're going to use the same layout again and again, put it in a separate style file and \usepackage{mylayouts} in each document.
Note: the package pgf is only needed to provide the command \pgfstroke. As all this does is draw a line, it may be possible to remove this in favour of a \rule of some sort.