cislovane OK

\documentclass[18pt,landscape]{article}
\usepackage{pdfpages}

\usepackage{pgfmath}
%\usepackage[margin=1cm,showframe]{geometry}% MWE only

\pgfmathsetmacro{\scale}{(\paperheight-2cm)/(\paperwidth-3cm)}% 1cm margin
\pgfmathsetlengthmacro{\delta}{\paperwidth-2cm-2*\scale*(\paperheight-3cm)-4mm}% 4mm fudge factor

%\usepackage{pdfpages} % <<<<<<<<<<<<<<<<<
\usepackage{fontspec}
\newfontfamily\hebfont{Arial}

%\usepackage{pdfpages} % <<<<<<<<<<<<<<<<<
\usepackage{fancyhdr}

\fancypagestyle{importedpages}{%
    \fancyhf{}% Clear header/footer
    \renewcommand{\headrulewidth}{0pt}% Remove header rule
    \renewcommand{\footrulewidth}{0pt}% Remove footer rule (default)  %
    \fancyfoot[C]{\raisebox{-\baselineskip}[100pt][200pt]{\thepage}}% Lower page number into position  % changed for this MWE  <<<<<
}

\fancypagestyle{Moreimportedpages}{%for this MWE <<<<
    \fancyhf{}% Clear header/footer
    \renewcommand{\headrulewidth}{3pt}%
    \renewcommand{\footrulewidth}{3pt}%
    \fancyfoot[C]{\color{red}\Huge\textbf{\thepage}}%
}

\fancypagestyle{Moreimportedpages2}{%for this MWE <<<<
    \fancyhf{}% Clear header/footer
    \renewcommand{\headrulewidth}{0pt}%
    \renewcommand{\footrulewidth}{0pt}%
    \fancyfoot[C]{{\hebfont\char\numexpr"05CF+\value{Acount}\relax}
\raisebox{-\baselineskip}[30pt][40pt]{\thepage}}%
}


%\begin{document}


\begin{document}

\includepdf[%
  nup=2x1,%  1 row; 2 cols
  pages=-,%
  delta=-10mm -10mm,%
  height=\dimeval{0.9\paperheight-20mm},%  scale: height - 2cm
  width=\dimeval{0.8\paperwidth-20mm},% scale: width/2 - 2cm
  keepaspectratio,% but don't distort
]{companion.pdf}
\end{document}

\end{document}


%    \newcounter{Acount}

%    \includepdf[scale=\scale,noautoscale,nup=2x1,pages=1-,delta={\delta} 0pt,
 %   offset=0pt -3mm,% offset in reverse order
  %  trim=2.5cm 2.5cm 5.5cm 2.5cm,
   % pages=-,
   % pagecommand=\thispagestyle{Moreimportedpages2} % added %<<<<<<<<<<<<<<<<<<<<<<<
    %\stepcounter{Acount}%
 %   Roman: \roman{Acount}\ %
  %  Hebrew {\hebfont\char\numexpr"05CF+\value{Acount}\relax},
   % ]{companion.pdf}



 %   \includepdf[scale=\scale,noautoscale,nup=2x2,pages=1-,delta={\delta} 0pt,
  %  offset=10pt -3mm,% offset in reverse order
   % trim=2.5cm 2.5cm 2.5cm 2.5cm,
    %pages=-,
   % pagecommand=\thispagestyle{Moreimportedpages2} % added %<<<<<<<<<<<<<<<<<<<<<<<
   % \stepcounter{Acount}%
%    Roman: \roman{Acount}\ %
%    Hebrew {\hebfont\char\numexpr"05CF+\value{Acount}\relax},
   % ]{companion.pdf}


\end{document}