What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
First, you need to identify the class or ID of the field you'd like to increase. Next, you can add a CSS code that will make the font size increase on that specific field. Next, you can inject the CSS code in to your form, this user guide will help you how to do CSS injection.
But to be able to help you further in detail, may I request the link to the form and also which part of the form is it that you wish to adjust its size?