Add a free text annotation to a PDF in UWP

To add a free text annotation to a PDF Document page.

PDFDoc doc = new PDFDoc(filename);
Page page = doc.GetPage(1);

// Create a free text
FreeText txtannot = FreeText.Create( doc, new Rect(100, 100, 350, 500)  );
txtannot.SetContentRect( new Rect( 200, 200, 350, 500 ) );
txtannot.SetContents( "\n\nSome swift brown fox snatched a gray hare out of the air by freezing it with an angry glare." +
                        "\n\nAha!\n\nAnd there was much rejoicing!" );
txtannot.SetCalloutLinePoints( new Point(200,300), new Point(150,290), new Point(110,110) );
txtannot.SetBorderStyle(new Annot.BorderStyle(Annot.BorderStyle.Style.e_solid, 1, 10, 20 ) );
txtannot.SetEndingStyle(Line.EndingStyle.e_ClosedArrow );
txtannot.SetColor( new ColorPt( 0, 1, 0 ) );
txtannot.SetQuaddingFormat(1);
page.AnnotPushBack(txtannot);
txtannot.RefreshAppearance();

Add or edit PDF annotations sample
Full code sample which shows how to add or edit PDF annotations (e.g. hyperlink, intra-document link, stamp, rubber stamp, file attachment, sound, text, free-text, line, circle, square, polygon, polyline, free text, squiggly, caret, and ink).