Measure remaining space on page and use it on another page

For more details

What is the difference between \def and \newcommand?

What is the difference between \let and \edef?

A solution is to use \edef method

\edef\measurepage{\the\dimexpr\pagegoal-\pagetotal-\baselineskip\relax}

MWE

\documentclass[a4paper,12pt]{article}

\usepackage[top=2cm,bottom=2cm,hmargin=2cm]{geometry}

\usepackage{lipsum}

\begin{document}

\section*{Firstpage}

\lipsum[1-4]

\edef\measurepage{\the\dimexpr\pagegoal-\pagetotal-\baselineskip\relax}

%%The value seems to be calculated correctly
\measurepage

\newpage

\section*{Secondpage}
%% Skip the measured space from the page before

\vfill

%%This is not the value stored above
\measurepage

\begin{minipage}[t][\measurepage][t]{\textwidth}
\lipsum[3]
\end{minipage}

\end{document}

This might work too. I use the existing definition of \measurepage, but set a new length, \remainder, to its value. I then use \remainder in the minipage argument.

\documentclass[a4paper,12pt]{article}
\usepackage[top=2cm,bottom=2cm,hmargin=2cm]{geometry}

\usepackage{lipsum}
\newlength\remainder
\newcommand\measurepage{\dimexpr\pagegoal-\pagetotal-\baselineskip\relax}
\begin{document}

\section*{Firstpage}

\lipsum[1-4]


%%The value seems to be calculated correctly
\remainder=\measurepage\relax\the\remainder

\newpage

\section*{Secondpage}
%% Skip the measured space from the page before

\vfill

%%This is not the value stored above
\the\measurepage

\begin{minipage}[t][\remainder][t]{\textwidth}
\lipsum[3]
\end{minipage}


\end{document}

You can get more exact values by storing the actuall positions in the aux-file. This need two compilations (the x are only there to show the locations):

\documentclass[a4paper,12pt]{article}

\usepackage[top=2cm,bottom=2cm,hmargin=2cm]{geometry}

\usepackage{lipsum}
\usepackage{zref-savepos}

\begin{document}

\section*{Firstpage}

\lipsum[1-4]

x\zsavepos{start}\par\vfill\mbox{x}\zsavepos{end}

\newpage

\section*{Secondpage}
%% Skip the measured space from the page before

\vfill

%the y position has its zero at the bottom
\begin{minipage}[t][\dimexpr\zposy{start}sp-\zposy{end}sp][t]{\textwidth}
\lipsum[3]\vfill xxxx
\end{minipage}


\end{document}