\newlength{\notesep}

\def\changemargin#1#2{\list{}{\rightmargin#2\leftmargin#1}\item[]}
\let\endchangemargin=\endlist 

\ifdefinedcolor{backsidecolor}{%
  \backgroundcolor{c[1]}{backsidecolor}
}{}

% Une commande dédiée pour les notes de marge
\newcommand{\DUsidebar}[1]{%
  \switchcolumn[0]
  \begin{changemargin}{0.5cm}{1cm} 
  \AltFont\selectfont
  \ifdefinedcolor{textsidecolor}{\color{textsidecolor}}{}
  #1
  \end{changemargin}
  \vspace{\notesep}
  \switchcolumn
  \ifdefinedcolor{textsidecolor}{\color{black}}{}
}

\AtBeginDocument{%
  \begin{paracol}{2}
}
\AtEndDocument{%
  % Make the column go to the bottom
  \flushpage
  \end{paracol}
}