Adding visible digital signatures to a PDF document

Use visible digital signatures to combine visual signoff with cryptographic integrity.

Common use cases include:

  • Contract signing workflows
  • Approval and authorization systems
  • Document authentication pipelines
  • Branded signature appearances

Unlike invisible signatures, visible signatures render content in a signature field on the page.

Download sample

How Nutrient helps

Nutrient Java SDK handles signature field operations, appearance generation, and cryptographic signing.

The SDK handles:

  • Parsing signature field dictionaries and appearance stream generation
  • Managing PKCS#12 certificate loading and private key extraction
  • Handling signature appearance customization and font rendering
  • Complex cryptographic signing operations and byte range calculations

Complete implementation

This example adds a visible signature field and signs it with different appearance options:

package io.nutrient.Sample;


import io.nutrient.sdk.Document;
import io.nutrient.sdk.types.Color;
import io.nutrient.sdk.editors.PdfEditor;
import io.nutrient.sdk.editors.pdf.pages.PdfPage;
import io.nutrient.sdk.editors.pdf.formfields.PdfSignatureField;
import io.nutrient.sdk.signing.PdfSigner;
import io.nutrient.sdk.signing.DigitalSignatureOptions;
import io.nutrient.sdk.signing.SignatureAppearance;


public class DigitalSignatures {

Create the main method as the sample entry point:

    public static void main(String[] args) {

Creating a signature field

Create a signature field before signing.

In this sample:

  • The field name is ApprovalSignature.
  • The position is (100, 700).
  • The size is 200 × 50.

Save the document after adding the field placeholder:

        try (Document document = Document.open("input.pdf")) {
            PdfEditor editor = PdfEditor.edit(document);
            PdfPage page = editor.getPageCollection().getFirst();


            PdfSignatureField signatureField = editor.getFormFieldCollection().addSignatureField(
                "ApprovalSignature",
                page,
                100.0f,   // left
                700.0f,   // top
                200.0f,   // width
                50.0f     // height
            );


            editor.saveAs("output_document_with_field.pdf");
            editor.close();
        } catch (Exception e) {
            System.err.println("Error creating signature field: " + e.getMessage());
        }

Signing with auto-generated appearance

Sign the field with an auto-generated visible appearance.

In this sample:

  • Document.open("output_document_with_field.pdf") opens the PDF containing the signature field.
  • DigitalSignatureOptions sets certificate path, password, and signer metadata.
  • setUseAutoGeneratedText(true) generates visible text from metadata.
  • setShowValidationMark(true) adds a validation icon.
  • signField(document, outputPath, fieldName, options, appearance) applies the digital signature and embeds the appearance.
        try (PdfSigner signer = new PdfSigner();
             Document document = Document.open("output_document_with_field.pdf")) {
            DigitalSignatureOptions options = new DigitalSignatureOptions();
            options.setCertificatePath("certificate.pfx");
            options.setCertificatePassword("Nutrient answers all your document needs");
            options.setSignerName("John Doe");
            options.setReason("Final Approval");
            options.setLocation("New York");


            SignatureAppearance appearance = new SignatureAppearance();
            appearance.setUseAutoGeneratedText(true);
            appearance.setShowValidationMark(true);


            signer.signField(
                document,
                "output_signed_visible.pdf",
                "ApprovalSignature",
                options,
                appearance
            );
        } catch (Exception e) {
            System.err.println("Error signing field: " + e.getMessage());
        }

Signing with a custom image

Use an image-based appearance for handwritten signatures or logos.

In this sample:

  • Document.open("output_document_with_field.pdf") opens the PDF before signing.
  • setImagePath(...) sets the signature image.
  • The image renders inside field bounds.
  • setShowValidationMark(true) keeps validation marks visible.
  • signField(document, outputPath, fieldName, options, appearance) applies the digital signature.
        try (PdfSigner signer = new PdfSigner();
             Document document = Document.open("output_document_with_field.pdf")) {
            DigitalSignatureOptions options = new DigitalSignatureOptions();
            options.setCertificatePath("certificate.pfx");
            options.setCertificatePassword("Nutrient answers all your document needs");
            options.setSignerName("Jane Smith");
            options.setReason("Review Complete");


            SignatureAppearance appearance = new SignatureAppearance();
            appearance.setImagePath("input_signature.jpg");
            appearance.setShowValidationMark(true);


            signer.signField(
                document,
                "output_signed_with_image.pdf",
                "ApprovalSignature",
                options,
                appearance
            );
        } catch (Exception e) {
            System.err.println("Error signing field: " + e.getMessage());
        }

Signing with custom text

Use custom text when you need workflow-specific signature content.

In this sample:

  • Document.open("output_document_with_field.pdf") opens the PDF before signing.
  • setUseAutoGeneratedText(false) disables metadata-generated text.
  • setText(...) sets the visible signature text.
  • \n creates multiline output.
  • signField(document, outputPath, fieldName, options, appearance) applies the digital signature.
        try (PdfSigner signer = new PdfSigner();
             Document document = Document.open("output_document_with_field.pdf")) {
            DigitalSignatureOptions options = new DigitalSignatureOptions();
            options.setCertificatePath("certificate.pfx");
            options.setCertificatePassword("Nutrient answers all your document needs");
            options.setSignerName("Manager");


            SignatureAppearance appearance = new SignatureAppearance();
            appearance.setUseAutoGeneratedText(false);
            appearance.setText("Approved by Management\nDate: 2024-01-15");


            signer.signField(
                document,
                "output_signed_custom_text.pdf",
                "ApprovalSignature",
                options,
                appearance
            );
        } catch (Exception e) {
            System.err.println("Error signing field: " + e.getMessage());
        }

Customizing text appearance

Customize typography to match document or brand requirements.

In this sample:

  • Document.open("output_document_with_field.pdf") opens the PDF before signing.
  • setFontName(...) sets the typeface.
  • setFontSize(...) sets text size.
  • setTextColor(...) applies ARGB color values.
  • signField(document, outputPath, fieldName, options, appearance) applies the digital signature.
        try (PdfSigner signer = new PdfSigner();
             Document document = Document.open("output_document_with_field.pdf")) {
            DigitalSignatureOptions options = new DigitalSignatureOptions();
            options.setCertificatePath("certificate.pfx");
            options.setCertificatePassword("Nutrient answers all your document needs");
            options.setSignerName("Executive");


            SignatureAppearance appearance = new SignatureAppearance();
            appearance.setUseAutoGeneratedText(false);
            appearance.setText("Approved by Executive Board");
            appearance.setFontName("Times New Roman");
            appearance.setFontSize(14.0f);
            appearance.setTextColor(Color.fromArgb(255, 0, 0, 128));  // Navy blue


            signer.signField(
                document,
                "output_signed_styled_text.pdf",
                "ApprovalSignature",
                options,
                appearance
            );
        } catch (Exception e) {
            System.err.println("Error signing field: " + e.getMessage());
        }
    }
}

Conclusion

Use this workflow to add visible digital signatures:

  1. Open the document using try-with-resources for automatic resource cleanup.
  2. Create a PDF editor and access the page collection.
  3. Add a signature field with addSignatureField() specifying the name, page, position (x, y), and dimensions (width, height).
  4. Save the document with the signature field placeholder.
  5. Configure DigitalSignatureOptions with the certificate path, password, signer name, reason, and location.
  6. Create a SignatureAppearance object to control visual presentation.
  7. Use setUseAutoGeneratedText(true) for automatic signature text generation from metadata.
  8. Use setImagePath() to embed custom signature images or logos.
  9. Use setText() with setUseAutoGeneratedText(false) for custom text content.
  10. Customize typography using setFontName(), setFontSize(), and setTextColor() with ARGB values.
  11. Use setShowValidationMark(true) to display validation checkmarks.
  12. Call signField() to perform cryptographic signing and embed appearance.

For related signing workflows, refer to the Java SDK guides.