/**
* Add the document metadata to the PDF.
*/
private void renderDocumentMetadata() {
final Galley areaTree = this.getAreaTree();
this.pdfDoc.setTitle(areaTree.getTitle());
this.pdfDoc.setAuthor(areaTree.getAuthor());
this.pdfDoc.setSubject(areaTree.getSubject());
this.pdfDoc.setKeywords(areaTree.getKeywords());
}