Twelf is a language used for describing and proving properties about logical systems. As part of a university project, I wrote a program able to translate parts of Twelf signatures into LaTeX, formatting definitions as either grammars or natural-deduction-tree-style inference rules. Proofs are not printed in any useful form, nor is more than second-order higher abstract syntax supported. While still in need of some final touchups and some documentation,
twelfppr is already somewhat useful. You can check out the code on the Github page.
As far as I know,
twelfppr should be able to handle the full Twelf language.