Using C# PDF SDK
C# PDF Builder: How to draw, add a line path to PDF file

...
PDFContext ctx = new PDFContext();
//  set figure size: width 600 pixels; height 100 pixels
ctx.SetWidth(new RELength(600, Units.PX));
ctx.SetHeight(new RELength(100, Units.PX));
//  draw a red line with 5px in width. 
ctx.DrawLine(new REPen(new REColor(255, 0, 0), 5F), 10, 10, 580, 80);
Figure figure = new Figure(ctx);
document.Add(figure);
...

String outputFilePath = Program.RootPath + "\\" + "Sample25.pdf";

Document document = new Document();
PDFBuildHandler.Create(document, outputFilePath);
//  open document
document.Open();
//  create Figure
PDFContext ctx = new PDFContext();
...
...
Figure figure = new Figure(ctx);
document.Add(figure);
//  close document and save to the output file
document.Close();