I suggest pure ascii text with no drawings, and drawings in separate
files in a format suitable for exact line drawings, as gif, tif, pcx,
or similar. Actual images in jpg format would be also allowed, but
only when essential. The drawings shall include captions and reference
to the text file that mentions the pictures. A single picture file may
contain several drawings. The text would have at the end a list of
drawings, listing unique file names given to them. An index file in
html could be prepared, with references to all the material.
No ascii pictures, and rigorous spelling check, please.
The great problem is with equations, that are treated as "advanced
material" by the software people (...) that didn't come out with
nothing more human-friendly that equations in programming languages.
I suggest Basic, that at least has an adequate exponential operator
(^), with nontrivial equations in picture files.
An alternative would be Postscript, that is also exact, allows
equations and pictures, and can be produced and printed easily.
PDF is little more than compressed Postscript, and Postscript can be
converted to PDF without any edition.
Antonio Carlos M. de Queiroz