essay = {
    "title": "",
    "author": { "fullname": "" },
    "intro": "",
    "conclusion": "",
    "paragraphs": [ { "paragraph": "" } ]
}

CreatePdf(){
    var docDefinition = {
      content: [
        { text: this.essay.title, style: 'header' },
        { text: new Date().toTimeString(), alignment: 'right' },

        { text: 'Written By : '+this.essay.author.fullname, style: 'subheader' },

        { text: this.essay.intro, style: 'story', margin: [0, 20, 0, 20] },

        // Foreach essay.paragraphs and display the value

        { text: this.essay.conclusion, style: 'story', margin: [0, 20, 0, 20] }
      ]
    }
    this.pdfObj = pdfMake.createPdf(docDefinition);
    this.pdfObj.download();
}

for(let parag of this.essay.paragraphs){
  console.log(parag.paragraph);
};