Mark required fields in PDF forms
Required fields in a PDF form have to say so in a way assistive technology reports. The flag lives in the Ff entry of the field's dictionary, and Acrobat Pro sets it from the Required checkbox in field properties. Put the word required in the tooltip too, so the field announces "Family name, required" rather than leaving the reader to infer it. A red asterisk drawn on the page is not enough on its own. W3C publishes PDF5 as a sufficient technique, and the technique includes what happens when someone submits an incomplete form. An alert has to describe the problem in text, not just refuse.
How we find it in an audit
We fill the form with a screen reader and listen to whether each mandatory field announces itself as required. Then we check the field properties and tooltips in Acrobat Pro, and try submitting an incomplete form to see what comes back. The check that matters most is the one people skip. Inspecting through the accessibility layer tells you whether the required flag is really set, or whether somebody typed the word into a label and left the field unflagged.
How affected users experience it
A screen reader user fills in what they can, submits, and gets rejected for skipping fields nothing ever described as mandatory. On paper-derived government forms this is common. The asterisk is a drawing, the legend explaining it sits at the bottom of the page, and the field itself says nothing.
Passes vs. fails
Passes
Each mandatory field has its Required property set and a tooltip reading "Family name (required)". A screen reader announces "Family name, required, edit text", and submitting early raises a spoken alert naming what is missing.
Fails
A visa application PDF marks mandatory fields with a red asterisk drawn next to the box. The fields' tooltips just say "Text field".
How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Error message describes invalid form field valueA tool finds candidates, you decide
Other ways to satisfy this rule
13 guides on this site are filed under 3.3.1 Error Identification. W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
- ARIA18sufficientRaise blocking errors in an alert dialog
- ARIA19sufficientAnnounce form errors with role=alert
- ARIA21sufficientFlag invalid fields with aria-invalid
- G83sufficientTell users which required fields they missed
- G84sufficientExplain when input is not an allowed value
- G85sufficientExplain format errors and show the fix
This guide is our interpretation of W3C technique PDF5: Indicating required form controls in PDF forms. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.