====== Firefox muestra fuentes ilegibles al imprimir ======

Para solucionar el problema(*) en Debian GNU/Linux, basta con instalar el paquete ttf-liberation. 

  apt-get install ttf-liberation

  apt-cache show ttf-liberation
  [...]
  Description: Free fonts with the same metrics as Times, Arial and Courier
  A set of serif, sans-serif and monospaced fonts from Red Hat with
  exactly the same metrics as the (non-free) Microsoft Times, Arial
  and Courier fonts, which implies those fonts can serve as a drop-in
  replacement. The font family is named Liberation.
  Homepage: https://fedorahosted.org/liberation-fonts/
  [...]

(*) Claro, todo depende de las fuentes que esté utilizando la página que se visualiza.