Adobe Acrobat - Prepare From - limiting word limit in text field

Simplest solution (does not take into account hyphenated words, line-breaks, etc.), is to use this code as the field's custom Keystroke event:

event.rc = AFMergeChange(event).split(" ").length<=500;

Note 1: The code will disappear when you enter it, due to a bug in Acrobat. It should still work, though.

Note 2: The user will be able to continue entering text into the field, but they won't be able to enter a space, then new text.

Note 3: A more complete solution will require a more complex code, of course.

Note 4: If you want to inform the user they reached the limit, enter this line after that code:

if (!event.rc) app.alert("You've reached the maximum amount of words allowed for this field.", 1);