.NETでPDFに注釈とフォームを追加する方法

using var doc = Document.Open(File.ReadAllBytes("input.pdf"));
var page = doc.Pages[1];

page.Annotations.AddTextAnnotation(
    new Rectangle(72, 720, 200, 740),
    contents: "Review this section",
    title: "Editor",
    open: true);

doc.Save("annotated.pdf");

var action = PdfAction.CreateUri("https://aspose.com");
page.Annotations.AddLinkAnnotation(
    new Rectangle(50, 700, 200, 720), action);

page.Annotations.AddHighlightAnnotation(
    new Rectangle(72, 680, 300, 700),
    quadPoints: null,
    color: new double[] { 1, 1, 0 });

page.Annotations.AddSquareAnnotation(
    new Rectangle(72, 640, 200, 680),
    borderColor: new double[] { 0, 0, 1 },
    fillColor: null,
    lineWidth: 1.5);

using var doc = Document.Open(pdfBytes);
foreach (var field in doc.Form.Fields)
{
    Console.WriteLine($"{field.FullName}: {field.Value}");
}

foreach (var annot in doc.Pages[1].Annotations)
{
    annot.Flatten();
}
doc.Save("flattened.pdf");