appendix.sty

% ---- Format sections ----

% Format section headings
\titleformat{\section}{\centering\large\bfseries}{Appendix~\thesection.}{1em}{}

% Format section labels
\renewcommand{\thesection}{\Alph{section}}

% Insert page break after each section
\newcommand{\sectionbreak}{\clearpage}

% ---- Add "A" in front of labels ----

\renewcommand{\thetheorem}{A\arabic{theorem}}
\renewcommand{\theproposition}{A\arabic{proposition}}
\renewcommand{\thelemma}{A\arabic{lemma}}
\renewcommand{\thecorollary}{A\arabic{corollary}}
\renewcommand{\thedefinition}{A\arabic{definition}}
\renewcommand{\theassumption}{A\arabic{assumption}}
\renewcommand{\theremark}{A\arabic{remark}}
\renewcommand{\thetable}{A\arabic{table}}
\renewcommand{\thefigure}{A\arabic{figure}}
\renewcommand{\theequation}{A\arabic{equation}}

% ---- Enable crossreferences ----

\usepackage{xr}