所谓墨痕注释即是客户在浏览PDF文件时随手涂鸦，就像看书时使用笔在书本上勾画重点一样，而在PDF阅读软件上要实现该功能怎么实现呢？Gnostice PDFOne .NET是一款PDF文档处理控件，可以帮助开发人员快速实现该功能，可以在阅读PDF文档时使用鼠标在PDF文档上进行墨痕注释，具体怎么实现可以参考下面的代码：

// Open a PDF document

PDFDocument doc = new PDFDocument(PDFOne_License.KEY);

doc.Load("USPTO_Catalog.pdf");

 

doc.MeasurementUnit = PDFMeasurementUnit.Inches;

 

// Create the ink annoation

PDFInkAnnot ink = new PDFInkAnnot();

ink.Title = "Ink annotation demo";

ink.Subject = "Annotation Demo";

ink.Content = "This is an ink annotation.";

ink.Vertices = 

new PointF[] {  

new PointF(6.7f,2.4f),

new PointF(4.2f,2.6f),

new PointF(4.15f,3f),

new PointF(5.2f,3.4f),

new PointF(5.7f,3.3f),

new PointF(6.5f,3.1f),

new PointF(6.5f,2.1f)

};

ink.LineColor = Color.Red;

ink.LineStyle = PDFAnnotLineStyle.Solid;

 

// Add the ink annotation to page 1

doc.CurrentPageNo = 1;

doc.AddAnnot(ink);

doc.Save("ink_annotation_demo.pdf");

doc.Close();