Set the margin and text size using geometry rather than TeX.

candidature.sty

@@ -5,18 +5,12 @@
 \usepackage{fontspec}
 \usepackage[french]{babel}
 \usepackage[backend=biber]{biblatex}
-
+\usepackage[
-% Resize the page to be close to what Sergey had in his HDR thesis.
+  text={154mm,253mm},
-\topmargin0.5cm
+  top=20mm,
-\oddsidemargin18.5mm
+  left=25mm,
-\evensidemargin7.5mm
+  twoside
-%\marginparsep0in
+]{geometry}
-%\marginparwidth0in
-%\textwidth15.92cm
-\textwidth139mm
-%\textheight23.5cm
-%\textheight212mm
-\textheight232mm
 
 % A thick horizontal rule filling all page width.
 \def\thickhrule{\leavevmode\leaders\hrule height 1.5pt\hfill\kern\z@}

candidature.tex

@@ -23,4 +23,5 @@
 \cite{Korec}
 
 Hello World
+
 \end{document}