Which TeX variant should I use to most easily create a custom invoice and a custom letter template?
I have a design for the invoice that I would like to implement exactly using a suitable TeX related system. It involves different fields at specific positions on the paper, a logo at a specific position, and a field with continuous text (the specification of the invoice) that has to be correctly word-wrapped. There are also some graphic lines at specified positions. The invoice will be in A4 format and must be able to accept at least different European alphabets/languages.
The letter also has a similar look and requirements.
I have used plain LaTeX in the past and I have also read a bit about the very many different systems and variants that are available, but it is confusing to try get an overview of what they can do.
Are anyone aware of what system I should have a look at to most easily create such templates? Also, it would be great if there was a tutorial available for creating such custom templates.
I'll try to make myself a bit more clear. My very basic understanding of TeX et. al. is that Donald Knuth wrote TeX as a very low level typesetting language. To make it a bit more manageable, Leslie Lamport started LaTeX which I understand to be a sort of macros defined for TeX to make it more comfortable/productive. However, my understanding is that in LaTeX, you are more or less constrained to the templates that you get. You can change some things but it seems to be quite static.
What I want to do is to set up a very detailed template comprising graphic elements such as lines and boxes that should appear at exactly specified places on the page. Then some of the boxes I would like to fill with text that should be typeset by some TeX engine.
Perhaps I have got it all wrong and this is already possible in LaTeX?
From the answers so far, it seems that perhaps LuaTeX could be a good bet considering the language requirements. However, can I do the above detailed graphical configuration of the page in Lua? If so, what constructs should I use and are you aware of anyone who did something similar and wrote a blog post or tutorial for it?