i know this is late response but you just gotta do this:
1- do what the addon tells u to: go to your Steam\steamapps\common\Left 4 Dead 2\left4dead2\cfg (if there is autoexec.cfg file just copy that command for me its (alias reloadfont "mat_setvideomode 1360 768 1; mat_setvideomode 1360 768 0") based on your game resolution).
2- open your console and put the same command in there.
3- just do reloadfont and it should hopefully work.