Create Digital signature field in iText Pdf - by Dustbiin

 Creating signature field in iText PDF - 

First need to add dependency 

<dependency>
   <groupId>com.itextpdf.tool</groupId>
   <artifactId>xmlworker</artifactId>
   <version>5.4.5</version>
</dependency>
<dependency>
   <groupId>com.itextpdf</groupId>
   <artifactId>itextpdf</artifactId>
   <version>5.4.5</version>
</dependency>
<dependency>
   <groupId>org.bouncycastle</groupId>
   <artifactId>bcprov-jdk15on</artifactId>
   <version>1.60</version>
</dependency>
<dependency>
   <groupId>org.bouncycastle</groupId>
   <artifactId>bcpkix-jdk15on</artifactId>
   <version>1.60</version>
   <type>jar</type>
   <!-- <scope>compile</scope>
   <optional>true</optional> -->
</dependency>

For certified you pdf document by digital sign first you need to create signature field in the document.

*Note -  Signature field name is very important we signature data on the basis of this field name 

Code for create signature field-

public class SignatureField{

    public static final String SRC           = "hello.pdf";
    public static final String SIGNAME       = "Signature1";

    public void createPdf( String filename )
        throws IOException,
        DocumentException,
        KeyStoreException,
        NoSuchAlgorithmException,
        CertificateException
    {
        // step 1: Create a Document
        Document document = new Document();
        // step 2: Create a PdfWriter
        PdfWriter writer = PdfWriter.getInstance( document, new FileOutputStream( filename ) );
        // step 3: Open the Document
        document.open();
        // step 4: Add content
        document.add( new Paragraph( "Hello World!" ) );
        // create a signature form field
        PdfFormField field = PdfFormField.createSignature( writer );
        // set Signature field name
        field.setFieldName( SIGNAME );
        // set the widget properties
        field.setPage();
        // set signature field position on the page
        field.setWidget( new Rectangle( 2, 732, 144, 780 ), PdfAnnotation.HIGHLIGHT_INVERT );
        field.setFlags( PdfAnnotation.FLAGS_PRINT );
        // add it as an annotation
        writer.addAnnotation( field );
        // maybe you want to define an appearance
        PdfAppearance tp = PdfAppearance.createAppearance( writer, 72, 48 );
        tp.setColorStroke( BaseColor.BLUE );
        tp.setColorFill( BaseColor.LIGHT_GRAY );
        tp.rectangle( 0.5f, 0.5f, 71.5f, 47.5f );
        tp.fillStroke();
        tp.setColorFill( BaseColor.BLUE );
        ColumnText.showTextAligned( tp, Element.ALIGN_CENTER, new Phrase( "SIGN HERE" ), 36, 24, 25 );
        field.setAppearance( PdfAnnotation.APPEARANCE_NORMAL, tp );
        BouncyCastleProvider provider = new BouncyCastleProvider();
        Security.addProvider( provider );
        // step 5: Close the Document
        document.close();
    }

        public static void main( String[] args )
            throws GeneralSecurityException,s
            IOException,
            DocumentException
        {
           SignatureField app = new SignatureField();
           app.createPdf( SRC );
        }
}

Output -