PDF stamp annotation in UWP

To create a stamp programmatically, instantiate a Stamp object just like any other annotation type and then call CreateAnnotationAsync on a Document:

var approvedStamp = new Stamp
{
BoundingBox = new Rect(10, 10, 400, 200),
StampType = StampType.Approved
};
await pdfView.Document.CreateAnnotationAsync(approvedStamp);
var customStamp = new Stamp
{
BoundingBox = new Rect(10, 300, 400, 200),
StampType = StampType.Custom,
Title = "A Title",
Subtitle = "A Subtitle",
Note = "A Note"
};
await pdfView.Document.CreateAnnotationAsync(customStamp);

You can also create a stamp from Instant JSON:

{
"bbox": [
10,
10,
400,
200
],
"stampType": "Custom",
"opacity": 1,
"pageIndex": 0,
"subtitle": "5/16/13, 10:34 AM",
"title": "Custom Stamp",
"type": "pspdfkit/stamp",
"v": 1
}
var stampJson = LoadJsonObjectAsync("myStamp.json");
var stamp = PSPDFKit.Pdf.Annotation.Factory.FromJson(stampJson);
await pdfView.Document.CreateAnnotationAsync(stamp);