Multiple pages with standalone

What I use is

\documentclass[multi=my,crop]{standalone}

After this, wrap every figure into \begin{my}…\end{my}.

I understand you already have some pdf figures, each one in an independent file and you want to obtain a booklet where each page shows one figure and each page is adjusted to figure size.

If my supposition is correct, you need incgraph package.

\documentclass{article}
\usepackage{incgraph}

\begin{document}

\incgraph{1943}

\incgraph{1842}

\end{document}

If you want to put fig1.pdf and fig2.pdf into a single PDF with each page exactly equal to the original pdf, then I recommend you use the pdftk program.

pdftk fig1.pdf fig2.pdf cat output newfile.pdf