Prohibit see-through text with gibberish on backside of page?

Question

I'd like to have the backside of my LaTeX pages printed with "gibberish" to prevent someone from holding the letter against a lamp and reading the see-through text. Kind of like the PIN letters have that banks send out when one gets a new debit-/credit card that has a new PIN going with it (somehow similar to this).

So, what I'd do if I knew how to is set up multiple "frames", each pretty much the size of the page itself, fill those with random letters and numbers, print them ontop of each other and misalign each by a few pixels, then print these on every second page...

Any help, as always, is highly appreciated.

This is what I go with now:

%Fontsize, Layout, papersize, type of document
\documentclass[12pt,oneside,a4paper]{scrartcl}

%margins
\renewcommand{\familydefault}{\sfdefault}
\usepackage{helvet}
\usepackage[left=0cm,right=0cm,top=1cm,bottom=1cm]{geometry}
\usepackage[cm]{fullpage}
\usepackage[nopar]{lipsum}

%header and footer (leaving this out yields a funny, ragged bottom)
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhf{}

%top line
\renewcommand{\headrulewidth}{0.5pt}

%footer centered
\fancyfoot[C]{\thepage}
%bottom line
\renewcommand{\footrulewidth}{0.5pt}

\newsavebox{\gibber}

\begin{document}

\savebox{\gibber}{\parbox{\linewidth}{\lipsum\lipsum}}
\vspace*{8cm}
\raisebox{0pt}[0pt][0pt]{\usebox{\gibber}}
\raisebox{-3pt}[0pt][0pt]{\usebox{\gibber}}\\
\raisebox{-5pt}[0pt][0pt]{\usebox{\gibber}}\\
\raisebox{-9pt}[0pt][0pt]{\usebox{\gibber}}\\
\hspace*{8pt}\raisebox{-12pt}[0pt][0pt]{\usebox{\gibber}}

\end{document}

Answer 1

You can overprint misaligned frames with raisebox. To get it placed on every second page, I would recommend creating your document normally (with a oneside option, perhaps), then inserting copies of this gibberish page between each page of your document with a command-line tool like pdfjam, which is included with TeX Live. (I don't know how to get LaTeX to output a given page for each even page.) Something like this would work:

pdfjam -o done.pdf -- myfile.pdf 1 gibber.pdf 1 myfile.pdf 2 gibber.pdf 1 myfile.pdf 3 gibber.pdf 1

Or, if you are using Bash, something like

pdfjam -o done.pdf -- $( for k in {1..15}; do echo myfile.pdf $k gibber.pdf 1; done )

where 15 is replaced by the number of pages, and myfile.pdf by the name of your file.

\documentclass{article}
\usepackage[cm]{fullpage}
\usepackage{lipsum}
\newsavebox{\gibber}
\begin{document}
\savebox{\gibber}{\parbox{\linewidth}{\lipsum\lipsum}}
\vspace*{8cm}
\raisebox{0pt}[0pt][0pt]{\usebox{\gibber}}
\raisebox{-4pt}[0pt][0pt]{\usebox{\gibber}}\\
\hspace*{8pt}\raisebox{-12pt}[0pt][0pt]{\usebox{\gibber}}
\end{document}