test.ts

@HostListener('window:documentViewerLoaded', ['$event'])
onDocumentViewerLoaded() {

  var signatureSettings = {
    showSignatureBar: true,
    redirectUrlAfterSignature: 'https://localhost:7122/document/customsign',
    ownerName: 'Paul',
    signerName: 'Jacob',
    signerInitials: 'PK',
    signatureBoxes: [{ name: 'txsign', signingRequired: true, style: 0 }]
  };

  this.http.get<DocumentData>('/document/prepare').subscribe(
    (result) => {
      this.documentData = result;
      console.log(this.documentData);
      TXDocumentViewer.loadDocument(this.documentData.document, this.documentData.name, signatureSettings);
    }
  );
  
}