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Technique PDF5:Indicating required form controls in PDF forms

About this Technique

This technique is Sufficient to meet 3.3.1: Error Identification and Sufficient to meet 3.3.2: Labels or Instructions when used with G131: Providing descriptive labels .


Tagged PDF documents with forms

This technique relates to:


The objective of this technique is to notify the user when a field that must be completed has not been completed in a PDF form. Required fields are implemented using the /Ff entry in the form field's dictionary. This is normally accomplished using a tool for authoring PDFs.

If errors are found, an alert dialog describes the nature of the error in text. This may be accomplished through scripting created by the author (see, for example, SCR18: Providing client-side validation and alert). User agents, such as Adobe Acrobat Pro and LiveCycle, can provide automatic alerts (as described in the examples below).

Once the user dismisses the alert dialog, it may be helpful if the script positions the keyboard focus on the field where the error occurred, although some users may expect the focus to remain on the last control focused prior to the alert appearing. Authors should exercise care to ensure that any movement of the focus will be expected. For example, if the alert announces a missing required phone number, positioning the focus on the phone number field when the alert is dismissed can be regarded as helpful and expected. In some cases, however, this may not be possible. If multiple input errors occur on the page, another approach must be taken to error reporting. (See, for example, the Adobe SDK.)

Ensuring that users are aware an error has occurred, can determine what is wrong, and can correct it are keys to software usability and accessibility. Meeting this objective helps ensure that all users can complete transactions with ease and confidence.

Labels for required form controls

It is also important that users are aware that an error may occur. You can incorporate this information in labels; for example, "Date (required)" or the use of a red asterisk to indicate required fields. (Make sure that a legend appears on each form with required fields, e.g., "* = required field".) See PDF10.


Example 1: Creating a required field in a PDF form using Acrobat Pro

  1. Open the Prepare Form tool, access the form field's context menu, and then select the Properties option.
  2. If the form field is required, check the Required box. This checkbox forces the user to fill in the selected form field. If the user attempts to submit the form while a required field is blank, an error message appears and the empty required form field is highlighted.
The Properties dialog for a form field. The Required box is checked on the First Name field.

This example is shown in operation in the working example of creating a required field in Acrobat.

Example 2: Adding a required text field in a PDF form using the /Tx field type and Ff flag

The following code fragment illustrates code that is typical for the object definitions for a typical text field. Note that the text field is required, using the Ff flag. This is typically accomplished by an authoring tool.

<< /AP -dict-                                                   
   /DA /Helv  0 Tf 0 g
   /DR -dict-
   /F 0x4
   /FT Tx              % FT key set to Tx for Text Field
   /Ff 0x2             % Ff integer 0x2 value indicates required
   /P -dict-
   /Rect -array-
   /StructParent 0x1
   /Subtype Widget
   /T First            % Partial field name First
   /TU First name (required)  % TU tool tip value serves as short description
   /Type Annot
   /V Pat Jones
<Start Stream>
  /P <</MCID 0 >>BDC
  /CS0 cs 0  scn 
  /TT0 1 Tf
   -0.001 Tc 0.003 Tw 11.04 0 0 11.04 72 709.56 Tm
   [(P)-6(le)-3(as)10(e)-3( )11(P)-6(rin)2(t)-3( Y)8(o)-7(u)2(r N)4(a)11(m)-6(e)]TJ
  0 Tc 0 Tw 9.533 0 Td
  ( )Tj
  -0.004 Tc 0.004 Tw 0.217 0 Td
   /P <</MCID 1 >>BDC
   0 Tc 0 Tw 4.283 0 Td
   [( )-2( )]TJ
    /ArtifactSpan <</MCID 2 >>BDC
    0.002 Tc -0.002 Tw 0.456 0 Td
    0 Tc 0 Tw 13.391 0 Td
    ( )Tj
<End Stream>	

Other sources

No endorsement implied.



For each form field that is required, verify that validation information and instructions are provided by applying the following:

  1. Check that the required status is indicated in the form control's label.
  2. Leave the field blank and submit the form. Check that an alert describing the error is provided.
  3. Use a tool that exposes the document through the accessibility API, and verify that the required property is indicated.

Expected Results

  • #1, #2, and #3 are true.
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