例のscaleboxなアレ

pxtatescale.sty

% pxtatescale.sty
\NeedsTeXFormat{pLaTeX2e}
\ProvidesPackage{pxtatescale}[2013/03/25 v0.2]
\def\pxqtg@pkgname{pxtatescale}
\@ifpackageloaded{graphics}{}{%else
  \PackageError\pxqtg@pkgname{Package 'graphics' not loaded}\@ehc}
\begingroup
\def\pxqtg@try@patch#1#2#3{%
  \def\pxqtg@temp{#2}\ifx#1\pxqtg@temp
    \gdef#1{#3}%
    \PackageInfo\pxqtg@pkgname{Patch applied to \string#1}%
  \else
    \PackageWarningNoLine\pxqtg@pkgname{Patch cannot be applied to \string#1}%
  \fi}
\pxqtg@try@patch\Grot@start
  {\special{pdf:btrans rotate \Grot@angle}}%
  {\special{pdf:btrans rotate \iftdir-\fi \Grot@angle}}
\pxqtg@try@patch\Gscale@start
  {\special{pdf:btrans xscale \Gscale@x\space yscale \Gscale@y}}%
  {\special{pdf:btrans
    \iftdir xscale \Gscale@y\space yscale \Gscale@x
    \else   xscale \Gscale@x\space yscale \Gscale@y
    \fi}}
\endgroup

test.tex

\documentclass[a5paper,10pt]{jsbook}

\usepackage{plext} % 縦書き拡張

\usepackage[dvipdfmx]{graphicx}
\usepackage{pxtatescale}

\begin{document}

scalebox のテスト。

\noindent\null
□\scalebox{1}[-1]{あ}□1,-1
\\
□\scalebox{-1}[1]{あ}□-1,1

\vspace{1cm}

\begin{minipage}<t>{4.5cm}
\noindent\null
□\scalebox{1}[-1]{あ}□1,-1
\\
□\scalebox{-1}[1]{あ}□-1,1
\end{minipage}

\end{document}