No license, no read-me, no description, no instructions, no compatibility info. Authors website does not appear to reference the plugin, but my french is pretty rusty. Okay, I don’t speak french at all, so it’s…really, really rusty.
There is no option page when activated (at least none I found), and the end result appears to be placing a margin over the header and a margin below the footer that inserts the visible text “header lex 7 -#” and “footer lex #” respectively. As you change posts and pages, it appears to change the “#” to the corresponding post or page id number.
Beyond that, I found no other functionality.
That was fun! ??