You can open your canvas data in anoter windows as printed format . where you can save it as pdf through ctrl+p
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
yourCanvasId.RenderControl(hw);
string canvasHTML = sw.ToString().Replace("\"", "'")
.Replace(System.Environment.NewLine, "");
StringBuilder sb = new StringBuilder();
sb.Append("<script type = 'text/javascript'>");
sb.Append("window.onload = new function(){");
sb.Append("var printWin = window.open('', '', 'left=0");
sb.Append(",top=0,width=1200,height=600,status=0');");
sb.Append("printWin.document.write(\"");
sb.Append(canvasHTML);
sb.Append("\");");
sb.Append("printWin.document.close();");
sb.Append("printWin.focus();");
sb.Append("printWin.print();");
sb.Append("printWin.close();};");
sb.Append("</script>");
ClientScript.RegisterStartupScript(this.GetType(), "CanvasPrint", sb.ToString());
Thanks
AARIF SHAIKH