# PDF Form Fields; charsize=auto?

I'm using hyperref to write a fillable form, but my users have a tendency to overfill the text boxes causing the text to be invisible on the printed sheet.

Acrobat allows for a definition of the character size in boxes to be "auto", that is, it will shrink the size of the font of the input text so that it fills the text box. However:

\documentclass[10pt]{article}
\usepackage{hyperref}

\begin{document}
\begin{Form}
\TextField[bordercolor=,width=10em,charsize=auto,name=box]{Thisisabox}
\end{Form}
\end{document}


does not compile, because hyperref requires that charsize be a number.

It is inconvenient to keep going into Acrobat every time I update the forms and manually set EVERY (there are dozens over 4 different forms) box individually to auto. Is there any easier way to do this using hyperref (or even Acrobat?)

Set charsize option to 0pt to get auto size for text fields:
\TextField[bordercolor=1 0 0,width=10em,charsize=0pt,name=box]{Thisisabox}