Java: Add or Delete Digital Signatures in PDF

With the rapid development of digital technologies, more and more companies create, store, and transmit information electronically. To ensure the credibility and authenticity of the electronic documents, digital signatures have been widely used. In this article, you will learn how to add an invisible or a visible digital signature to PDF and how to remove digital signatures from PDF by using Spire.PDF for Java.

Install Spire.PDF for Java

First, you're required to add the Spire.Pdf.jar file as a dependency in your Java program. The JAR file can be downloaded from this link. If you use Maven, you can easily import the JAR file in your application by adding the following code to your project's pom.xml file.

<repositories>
    <repository>
        <id>com.e-iceblue</id>
        <name>e-iceblue</name>
        <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
    </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.pdf</artifactId>
        <version>8.11.8</version>
    </dependency>
</dependencies>
    

Add an Invisible Digital Signature to PDF

The following are the steps to add an invisible digital signature to PDF using Spire.PDF for Java.

  • Create a PdfDocument object.
  • Load a sample PDF file using PdfDocument.loadFromFile() method.
  • Load a pfx certificate file while initializing the PdfCertificate object.
  • Create a PdfSignature object based on the certificate.
  • Set the document permissions using PdfSignature. setDocumentPermissions() method.
  • Save the document to another PDF file using PdfDocument.saveToFile() method.
  • Java
import com.spire.pdf.PdfDocument;
import com.spire.pdf.security.PdfCertificate;
import com.spire.pdf.security.PdfCertificationFlags;
import com.spire.pdf.security.PdfSignature;

public class AddInvisibleSignature {

    public static void main(String[] args) {

        //Create a PdfDocument object
        PdfDocument doc = new PdfDocument();

        //Load a sample PDF file
        doc.loadFromFile("C:\\Users\\Administrator\\Desktop\\Java PDF.pdf");

        //Load a pfx certificate
        PdfCertificate cert = new PdfCertificate("C:\\Users\\Administrator\\Desktop\\MyCertificate.pfx", "e-iceblue");

        //Create a PdfSignature object
        PdfSignature signature = new PdfSignature(doc, doc.getPages().get(doc.getPages().getCount() - 1), cert, "MySignature");

        //Set the document permission to forbid changes but allow form fill
        signature.setDocumentPermissions(PdfCertificationFlags.Forbid_Changes);
        signature.setDocumentPermissions(PdfCertificationFlags.Allow_Form_Fill);

        //Save to another PDF file
        doc.saveToFile("output/InvisibleSignature.pdf");
        doc.close();
    }
}

Java: Add or Delete Digital Signatures in PDF

Add a Visible Digital Signature to PDF

The following are the steps to add a visible digital signature to PDF using Spire.PDF for Java.

  • Create a PdfDocument object.
  • Load a sample PDF file using PdfDocument.LoadFromFile() method.
  • Load a pfx certificate file while initializing the PdfCertificate object.
  • Create a PdfSignature object and specify its position and size on the document.
  • Set the signature details including date, name, location, reason, handwritten signature image, and document permissions.
  • Save the document to another PDF file using PdfDocument.SaveToFile() method.
  • Java
import com.spire.pdf.PdfDocument;
import com.spire.pdf.graphics.PdfFont;
import com.spire.pdf.graphics.PdfFontFamily;
import com.spire.pdf.graphics.PdfFontStyle;
import com.spire.pdf.graphics.PdfImage;
import com.spire.pdf.security.GraphicMode;
import com.spire.pdf.security.PdfCertificate;
import com.spire.pdf.security.PdfCertificationFlags;
import com.spire.pdf.security.PdfSignature;

import java.awt.*;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;

public class AddVisibleSignature {

    public static void main(String[] args) {

        //Create a PdfDocument object
        PdfDocument doc = new PdfDocument();

        //Load a sample PDF file
        doc.loadFromFile("C:\\Users\\Administrator\\Desktop\\Java PDF.pdf");

        //Load a pfx certificate
        PdfCertificate cert = new PdfCertificate("C:\\Users\\Administrator\\Desktop\\MyCertificate.pfx", "e-iceblue");

        //Create a PdfSignature object and specify its position and size
        PdfSignature signature = new PdfSignature(doc, doc.getPages().get(0), cert, "MySignature");
        Rectangle2D rect = new Rectangle2D.Float();
        rect.setFrame(new Point2D.Float((float) doc.getPages().get(0).getActualSize().getWidth() - 320, (float) doc.getPages().get(0).getActualSize().getHeight() - 140), new Dimension(270, 100));
        signature.setBounds(rect);

        //Set the graphics mode
        signature.setGraphicMode(GraphicMode.Sign_Image_And_Sign_Detail);

        //Set the signature content
        signature.setNameLabel("Signer:");
        signature.setName("Gary");
        signature.setContactInfoLabel("ContactInfo:");
        signature.setContactInfo("02881705109");
        signature.setDateLabel("Date:");
        signature.setDate(new java.util.Date());
        signature.setLocationInfoLabel("Location:");
        signature.setLocationInfo("Chengdu");
        signature.setReasonLabel("Reason: ");
        signature.setReason("The certificate of this document");
        signature.setDistinguishedNameLabel("DN: ");
        signature.setDistinguishedName(signature.getCertificate().get_IssuerName().getName());
        signature.setSignImageSource(PdfImage.fromFile("C:\\Users\\Administrator\\Desktop\\handwrittenSignature.png"));

        //Set the signature font
        signature.setSignDetailsFont(new PdfFont(PdfFontFamily.Helvetica, 10f, PdfFontStyle.Regular));

        //Set the document permission
        signature.setDocumentPermissions(PdfCertificationFlags.Forbid_Changes);
        signature.setCertificated(true);

        //Save to file
        doc.saveToFile("output/VisibleSignature.pdf");
        doc.close();
    }
}

Java: Add or Delete Digital Signatures in PDF

Remove Digital Signatures from PDF

The following are the steps to remove digital signatures from PDF using Spire.PDF for Java.

  • Create a PdfDocument object.
  • Get form widgets from the document using PdfDocument.getForm() method.
  • Loop through the widgets and determine if a specific widget is a PdfSignatureFieldWidget.
  • Remove the signature widget using PdfFieldCollection.remove() method.
  • Save the document to another PDF file using PdfDocument.saveToFile() method.
  • Java
import com.spire.pdf.PdfDocument;
import com.spire.pdf.widget.PdfFieldWidget;
import com.spire.pdf.widget.PdfFormWidget;
import com.spire.pdf.widget.PdfSignatureFieldWidget;

public class DeleteSignatures {

    public static void main(String[] args) {

        //Create a PdfDocument object
        PdfDocument doc = new PdfDocument("C:\\Users\\Administrator\\Desktop\\VisibleSignature.pdf");

        //Get form widgets from the document
        PdfFormWidget widgets = (PdfFormWidget) doc.getForm();

        //Loop through the widgets
        for (int i = 0; i < widgets.getFieldsWidget().getList().size(); i++)
        {
            //Get a specific widget
            PdfFieldWidget widget = (PdfFieldWidget)widgets.getFieldsWidget().getList().get(i);

            //Determine if the widget is a PdfSignatureFieldWidget
            if (widget instanceof PdfSignatureFieldWidget)
            {
                //Remove the signature widget
                widgets.getFieldsWidget().remove(widget);;
            }
        }

        //Save the document to another PDF file
        doc.saveToFile("output/DeleteSignatures.pdf");
    }
}

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