[Checkpoint] 3.3.6 Error Prevention (All): For Web pages that require the user to submit information, at least one of the following is true: (Level AAA) Reversible: Submissions are reversible. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission. [Comments] 
No Accessibility Support impact. This is design-specific. Application or document authors need to consider this provision and ensure conformance. In such forms, PDF authors are able to utilize validation or server-side error-checking prior to final submission.