\documentclass[letterpaper, 12pt]{article}
\usepackage{pdfpages}
\usepackage{changepage}
\usepackage{fancyhdr}

\setlength\topmargin{-0.675in}
\setlength\textheight{7.0in}
\setlength\textwidth{7.0in}
\setlength\oddsidemargin{-0.25in}
\setlength\evensidemargin{-0.25in}

\strictpagecheck

\thispagestyle{empty}
\fancypagestyle{mystyle}{
    % hide any background elements in source PDF with \colorbox{white} %
    \fancyhead[C]{\colorbox{white}\vartitle}
    \fancyhead[R]{\colorbox{white}{Page \thepage}}
    \fancyfoot[C]{} % Remove default page number footer %
}

\begin{document}
    \includepdf[pages=-,pagecommand={\thispagestyle{mystyle}}]\varinput
\end{document}