Use any letterhead in LaTeX

content/tips-letterhead.md

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+---
+Title: Use any letterhead in LaTeX
+Date: 2019-04-22 20:00
+Author: Fabrice
+Category: tips
+Slug: latex-letterhead
+Header_Cover: images/cover_palace.jpg
+---
+
+It sometimes appear that I have to write some official documents from some entities, especially for admin stuff.
+However, those letterheads are often provided in some [proprietary format](https://en.wikipedia.org/wiki/Office_Open_XML) with which I do my best to make as few interactions as possible.
+Especially, I feel more comfortable editing some LaTeX instead of writting it in [libreoffice](https://libreoffice.org/) (for instance).
+
+Thus, thanks to [Nicolas Trotignon](https://perso.ens-lyon.fr/nicolas.trotignon/) who found a simple workaround, here is a small trick to do it.
+As a preliminary, you have to obtain a pdf version of the letterhead (to do so, I'm using [online office 365](https://en.wikipedia.org/wiki/Office_365) as it works in Linux, yes, shame on me).
+
+Once this is done, the core of this method is to use the `wallpaper` package to embed the letterhead as a background image, and then play with margins to make it look nice.
+
+Here follows a minimal example with the [corresponding output](examples/background-latex.pdf). Replace `background.pdf` with your (empty) letterhead of course.
+This can also be adapted to other classes, such as [`letter.cls`](https://ctan.org/pkg/letter).
+
+```tex
+\documentclass[a4paper]{article}
+% Design and encoding stuff
+\usepackage[utf8]{inputenc}
+\usepackage[UKenglish]{babel}
+\usepackage[T1]{fontenc}
+\usepackage{libertine}
+% The main trick
+\usepackage{wallpaper}
+\CenterWallPaper{1}{background.pdf}
+% margin
+\usepackage[inner=4.5cm,top=6cm]{geometry}
+\begin{document}
+% blabla
+Hello, World!
+% …
+\end{document}
+
+```
+