I don't think you can do that with Acrobat Forms. You can make the type scroll and you can make the type go to a smaller size to fit the box by selecting "Auto" under size. Not that I think that these are satisfactory solutions.
To clarify Derek's "I don't think so", his answer is correct with what you can do in both InDesign and in Acrobat.
Either that or let it scroll.
Yes, you can scroll but that's only good for end-users viewing the form on-screen, the whole text wouldn't print out (as you know of course).
If you make an interactive fillable form, you would have a fixed content area for any comment. Once someone exceeds the fillable area you get a scroll option and the content can be scrolled and seen.
If you need to enlarge the content area instead of the scroll option, I believe you need to use AEM Forms Designer formerly Adobe LifeCycle Designer, for that, wherein you can create dynamic PDF. Please check these links:
If you need to enlarge the content area instead of the scroll option, I believe you need to use AEM Forms Designer formerly Adobe LifeCycle Designer, for that, wherein you can create dynamic PDF.
Now that LiveCycle Designer has become AEM Forms Designer, is it also available for Mac?
The last information I heard is that LifeCycle Designer apparently will never be available for the Mac. It's also a deprecated application. Adobe put their focus on Acro forms with Acrobat XI and Acrobat DC. They discontinued incuding LifeCycle Designer with Acrobat.
They apparently have farmed it out only to Enterprise users who still need it.
It wouldn't be available to "normal" users to purchase or subscribe to. Here's a quote from an Experience staff member in another forum:
"As far as i'm aware, credit card are not used for payment on experience cloud. You'd need a pretty high limit to pay the tens of thousands if not millions of dollars that each company pays."
If someone has more "experience" with it, I'd like to hear about it.