Free Spire.PDF for .NET 4.3（社区版）
using Spire.Pdf;using Spire.Pdf.Annotations;using Spire.Pdf.Annotations.Appearance;using Spire.Pdf.Graphics;using System;using System.Drawing; namespace AddStamp_PDF{ class Program { static void Main(string[] args) { //创建一个PdfDocument类对象，并加载PDF文档 PdfDocument doc = new PdfDocument(); doc.LoadFromFile(@'C:\Users\Administrator\Desktop\test.pdf'); //获取PDF文档第一页 PdfPageBase page = doc.Pages[0]; //新建一个PdfRubberStampAnnotation对象，指定其注释的位置和大小 PdfRubberStampAnnotation loStamp = new PdfRubberStampAnnotation(new RectangleF(new PointF(-5, -5), new SizeF(200, 200))); //实例化一个PdfAppearance对象，并加载作为印章的图片 PdfAppearance loApprearance = new PdfAppearance(loStamp); PdfImage image = PdfImage.FromFile(@'C:\Users\Administrator\Desktop\yz.jpg'); //新建一个PDF模板，并在模板里绘制图片 PdfTemplate template = new PdfTemplate(600, 800); template.Graphics.DrawImage(image, 0, 0); loApprearance.Normal = template; loStamp.Appearance = loApprearance; //添加印章到PDF文档 page.AnnotationsWidget.Add(loStamp); //保存并打开文档 string output = 'ImageStamp.pdf'; doc.SaveToFile(output); System.Diagnostics.Process.Start('ImageStamp.pdf'); } }}