Demo 16 was updated to show how page number types format and start work.

demo/demo16.ts

@@ -1,7 +1,7 @@
 // Multiple sections and headers
 // Import from 'docx' rather than '../build' if you install from npm
 import * as fs from "fs";
-import { Document, Packer, PageNumberFormat, PageOrientation, Paragraph } from "../build";
+import { Document, Packer, PageNumberFormat, PageOrientation, Paragraph, TextRun } from "../build";
 
 const doc = new Document();
 
@@ -41,6 +41,40 @@ doc.addSection({
 
 doc.createParagraph("hello in landscape");
 
+const header2 = doc.createHeader();
+const pageNumber = new TextRun("Page number: ").pageNumber(); 
+header2.createParagraph().addRun(pageNumber);
+
+doc.addSection({
+    headers: {
+        default: header2,
+    },
+    orientation: PageOrientation.PORTRAIT,
+});
+
+doc.createParagraph("Page number in the header must be 2, because it continues from the previous section.");
+
+doc.addSection({
+    headers: {
+        default: header2,
+    },
+    pageNumberFormatType: PageNumberFormat.UPPER_ROMAN,
+    orientation: PageOrientation.PORTRAIT,
+});
+
+doc.createParagraph("Page number in the header must be III, because it continues from the previous section, but is defined as upper roman.");
+
+doc.addSection({
+    headers: {
+        default: header2,
+    },
+    pageNumberFormatType: PageNumberFormat.DECIMAL,
+    pageNumberStart: 25,
+    orientation: PageOrientation.PORTRAIT,
+});
+
+doc.createParagraph("Page number in the header must be 25, because it is defined to start at 25 and to be decimal in this section.");
+
 const packer = new Packer();
 
 packer.toBuffer(doc).then((buffer) => {