[Checkpoint] 3.3.3 Error Suggestion: If an input error is automatically detected and suggestions for correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content. (Level AA) [Comments] 
PDF form controls that accept user input provide validation functionality which can alert the user of the error in text. PDF supports scripting functionality which allows customization of error responses, enabling the provision of suggestions when possible.