This example was written in answer to the question Click How to underline a portion of text in a text field?
fillwithunderline
##GITHUB:https://github.com/itext/i7js-examples/blob/develop/src/main/java/com/itextpdf/samples/sandbox/acroforms/FillWithUnderline.java##
##GITHUB:https://github.com/itext/i7ns-samples/blob/develop/itext/itext.samples/itext/samples/sandbox/acroforms/FillWithUnderline.cs##
Resources
https://github.com/itext/i7js-examples/blob/develop/src/main/resources/pdfs/form.pdf