Yes. It's a bit tricky though and you'd need custom firmware.
You need to add the following to the environemnt vars of the kconfig.xml:
Code:
<!-- Trick to change the scaling factor -->
<variable name="bbebTextScale-1" value="95"/>
<variable name="bbebTextScale0" value="100"/>
<variable name="bbebTextScale1" value="105"/>
<variable name="bbebTextScale2" value="110"/>
<variable name="bbebTextScale3" value="115"/>
<variable name="bbebTextScale4" value="120"/>
<!-- Trick to change the scaling factor -->
It's kind of built-in into PRS+ but I'm actually thinking of axing this feature as it only works if user also did that and didn't do that, which is hard to expect from average user.