I would like to modify the fonts used in that document which used \usepackage{mathptmx}. I thought it could possible using Xelatex, but I don't know to do it. This is my MWE :
\documentclass[10pt,foldmark,notumble]{leaflet}
\usepackage[utf8]{inputenc}
\usepackage[frenchb]{babel}
\renewcommand*\foldmarkrule{.3mm}
\renewcommand*\foldmarklength{5mm}
\usepackage{url}
\usepackage{amsmath}
\usepackage[T1]{fontenc}
\usepackage{textcomp}
\usepackage{mathptmx}
\usepackage[scaled=0.9]{helvet}
\makeatletter
\begin{document}
\maketitle
\end{document}
