Something else to consider, if you want to have expandable text fields, you'll need to save your document as a dynamic .pdf. Static .pdf's will still leave you with a small "+" sign in the lower right corner of the text field if the user fills all the available space and continues to type. You may want to consider putting in a script to limit the scrolling of text fields, so that the user cannot type beyond the limits of the field.
For example:
var myDoc = event.target;
var f = myDoc.getField("formname[0].subformname[0].fieldname[0]");
f.doNotScroll = true;
Put this script into the initialize event of the field you want to limit the scrolling of, and change the names to match the field you want to specify.