xdotool and xbindkeys

I have an Acrobat reader that does not zoom on Control+plus but rather on Control+acute (Control-plus annoyingly rotates the document).

I would like to fix this using xbindkeys and xdotool but the complication is that Control-plus is also used by other applications.

So the idea is to intercept Control-plus, check if Acrobat is the active window. If so send Acrobat a Control-acute, otherwise send the Control-plus.

Here my current attempt for the script that xbindkeys starts on Control+plus:

WM_CLASS=$(xprop -id `xdotool getactivewindow` WM_CLASS |awk '{print $4}')

if [ "$WM_CLASS" = "\"Acroread"\" ];
then
   sleep 0.1s;
   xdotool key --clearmodifiers ctrl+acute
else
   killall xbindkeys
   xdotool key --clearmodifiers ctrl+plus
   xbindkeys
fi

This actually works but the problem is that if I would not kill xbindkeys than xdotool sending ctrl-plus would again trigger xbindkeys and so on.

But of course this means that every time I hit Control+plus in a non-acrobat window xbindkeys needs to be killed and restarted...

Is there a better way to do this?

Many thanks!