When form fields are logically grouped together (especially radio buttons and checkboxes), non-visual users need access to both prompts. For example, in the following set of radio buttons, users need to know that "Computer Science" is a label associated with the first radio button, but that alone would not give them enough information to answer the question. They also need to know that "Select a major" is the overall prompt.
In HTML, use fieldset and legend
<legend>Select a major:</legend>
<input type=“radio” name=“major” id=“maj1”>
<label for=“maj1”>Computer Science</label>
<!-- etc. -->
In PDF, use tooltip like legend
And “Radio Button Choice” like label