Digital Signatures

const wvElement = document.getElementById('viewer');
WebViewer({ 
  fullAPI: true,
  ...options 
  }, wvElement)
  .then(instance => {
    const { PDFNet, docViewer, annotManager } = instance;
    const xfdfString = await annotManager.exportAnnotations();
    const data = await docViewer.getDocument().getFileData({ xfdfString });
    await PDFNet.initialize();
    await PDFNet.runWithCleanup(async () => {
      const doc = await PDFNet.PDFDoc.createFromBuffer(new Uint8Array(data));
      doc.lock();
      // Add an StdSignatureHandler instance to PDFDoc, making sure to keep track of it using the ID returned.
      const sigHandlerId = await doc.addStdSignatureHandlerFromURL(cert_file_path, 'password');
      sign() { // approval signature
        // Retrieve the unsigned approval signature field.
        /**
         * Note: Replace approvalFieldName with the field name in the document
         * that is being signed and approved
         */
        const foundApprovalField = await doc.getField(approvalFieldName);
        const approvalSigField = await PDFNet.DigitalSignatureField.createFromField(foundApprovalField);
        // (OPTIONAL) Add more information to the signature dictionary.
        await approvalSigField.setLocation("Vancouver, BC");
        await approvalSigField.setReason("Document approval.");
        await approvalSigField.setContactInfo("www.pdftron.com");
        // (OPTIONAL) Add an appearance to the signature field.
        const img = await PDFNet.Image.createFromURL(doc, appearance_img_path);
        const approvalSignatureWidget = await PDFNet.SignatureWidget.createWithDigitalSignatureField(doc, await PDFNet.Rect.init(0, 100, 200, 150), approvalSigField);
        await approvalSignatureWidget.createSignatureAppearance(img);
        const page1 = await doc.getPage(1);
        page1.annotPushBack(approvalSignatureWidget);
        // Prepare the signature and signature handler for signing.
        await approvalSigField.signOnNextSaveWithCustomHandler(sigHandlerId);
        // The actual approval signing will be done during the following incremental save operation.
        const buf = await doc.saveMemoryBuffer(0);
        const blob = new Blob([buf], { type: 'application/pdf' });
        saveAs(blob, 'signed_doc.pdf');
      }
      certify() { // certification signature
        /**
         * Certifying a document requires a digital signature field (can optionally be
         * hidden), hence why the logic below either looks for an existing field in the
         * document, or suggests creating a field in the document
         */
        // Retrieve the unsigned certification signature field.
        /**
         * Note: Replace certificationFieldName with the field name in the
         * document that is being certified
         */
        const foundCertificationField = await doc.getField(certificationFieldName);
        const certificationSigField = await PDFNet.DigitalSignatureField.createFromField(foundCertificationField);
        // Alternatively, create a new signature form field in the PDFDoc. The name argument is optional;
        // leaving it empty causes it to be auto-generated. However, you may need the name for later.
        // Acrobat doesn't show digsigfield in side panel if it's without a widget. Using a
        // Rect with 0 width and 0 height, or setting the NoPrint/Invisible flags makes it invisible.
        // const certificationSigField = await doc.createDigitalSignatureField(certificationFieldName);
        // (OPTIONAL) Add more information to the signature dictionary.
        await certificationSigField.setLocation("Vancouver, BC");
        await certificationSigField.setReason("Document certification.");
        await certificationSigField.setContactInfo("www.pdftron.com");
        // (OPTIONAL) Add an appearance to the signature field.
        const img = await PDFNet.Image.createFromURL(doc, appearance_img_path);
        const certifySignatureWidget = await PDFNet.SignatureWidget.createWithDigitalSignatureField(doc, await PDFNet.Rect.init(0, 100, 200, 150), certificationSigField);
        await certifySignatureWidget.createSignatureAppearance(img);
        const page1 = await doc.getPage(1);
        page1.annotPushBack(certifySignatureWidget);
        // Prepare the document locking permission level to be applied upon document certification.
        certificationSigField.setDocumentPermissions(PDFNet.DigitalSignatureField.DocumentPermissions.e_no_changes_allowed);
        
        // Prepare the signature and signature handler for certification.
        await certificationSigField.certifyOnNextSaveWithCustomHandler(sigHandlerId);
        // Save the PDFDoc. Once the method below is called, PDFNet will also certify the document using the information provided.
        const buf = await doc.saveMemoryBuffer(0);
        const blob = new Blob([buf], { type: 'application/pdf' });
        saveAs(blob, 'certified_doc.pdf');
      })
    })
  })