PdfDocument doc = new PdfDocument();
doc.LoadFromFile("To a Skylark.pdf");

PdfPageBase page = doc.Pages[0];

System.Drawing.Image backgroundImage = System.Drawing.Image.FromFile("Sky.jpg");
page.BackgroundImage = backgroundImage;

doc.SaveToFile("With Background Image.pdf");
System.Diagnostics.Process.Start("With Background Image.pdf");

using System.Windows;
using Spire.Pdf;

namespace Poetic_Works
{
    /// 
    /// Interaction logic for MainWindow.xaml
    /// 
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void button2_Click(object sender, RoutedEventArgs e)
        {
            PdfDocument doc = new PdfDocument();
            doc.LoadFromFile("To a Skylark.pdf");
            PdfPageBase page = doc.Pages[0];
            System.Drawing.Image backgroundImage = System.Drawing.Image.FromFile("Sky.jpg");
            page.BackgroundImage = backgroundImage;
            doc.SaveToFile("With Background Image.pdf");
            System.Diagnostics.Process.Start("With Background Image.pdf");
        }
    }
}

Imports System.Windows
Imports Spire.Pdf

Namespace Poetic_Works
	''' 
	''' Interaction logic for MainWindow.xaml
	''' 
	Public Partial Class MainWindow
		Inherits Window
		Public Sub New()
			InitializeComponent()
		End Sub

		Private Sub button2_Click(sender As Object, e As RoutedEventArgs)
			Dim doc As New PdfDocument()
			doc.LoadFromFile("To a Skylark.pdf")
			Dim page As PdfPageBase = doc.Pages(0)

			Dim backgroundImage As System.Drawing.Image = System.Drawing.Image.FromFile("Sky.jpg")
			page.BackgroundImage = backgroundImage
			doc.SaveToFile("With Background Image.pdf")
			System.Diagnostics.Process.Start("With Background Image.pdf")
		End Sub
	End Class
End Namespace

using System.Drawing;
using System.Windows;
using Spire.Pdf;
using Spire.Pdf.Annotations;
using Spire.Pdf.Graphics;

PdfDocument doc = new PdfDocument();
PdfPageBase page = doc.Pages.Add();

PdfFont font = new PdfFont(PdfFontFamily.TimesRoman, 15);
string text = "Spire.PDF";
PdfSolidBrush brush = new PdfSolidBrush(Color.DeepSkyBlue);
PointF point = new PointF(50, 100);
page.Canvas.DrawString(text, font, brush, point);

PdfTextMarkupAnnotation annotation = new PdfTextMarkupAnnotation("Author", "Demo", text, new PointF(0, 0), font);

“Author”: the author of annotation.
“Demo”: text content of annotation.
text: the text which will be marked.
new PointF(0, 0): not supported at present.
font: the font of the text which will be marked.

annotation.Border = new PdfAnnotationBorder(0.50f);
annotation.TextMarkupColor = Color.LemonChiffon;
annotation.Location = new PointF(point.X + doc.PageSettings.Margins.Left, point.Y + doc.PageSettings.Margins.Left);

(page as PdfNewPage).Annotations.Add(annotation);

(page as PdfNewPage).Annotations[0].Text = "This is an annotation";

doc.SaveToFile("Annotation.pdf");
System.Diagnostics.Process.Start("Annotation.pdf");

private void button1_Click(object sender, RoutedEventArgs e)
{
    PdfDocument doc = new PdfDocument();
    PdfPageBase page = doc.Pages.Add();
    PdfFont font = new PdfFont(PdfFontFamily.TimesRoman, 15);
    string text = "Spire.PDF";
    PdfSolidBrush brush = new PdfSolidBrush(Color.DeepSkyBlue);
    PointF point = new PointF(50, 100);
    page.Canvas.DrawString(text, font, brush, point);
    
    //Add annotation
    PdfTextMarkupAnnotation annotation = new PdfTextMarkupAnnotation("Author", "Demo", text, new PointF(0, 0), font);
    annotation.Border = new PdfAnnotationBorder(0.50f);
    annotation.TextMarkupColor = Color.LemonChiffon;

    annotation.Location = new PointF(point.X + doc.PageSettings.Margins.Left, point.Y + doc.PageSettings.Margins.Left);
(page as PdfNewPage).Annotations.Add(annotation);

    //Edit the text of the annotation
    (page as PdfNewPage).Annotations[0].Text = "This is an annotation";

    doc.SaveToFile("Annotation.pdf");
System.Diagnostics.Process.Start("Annotation.pdf");
}

PdfDocument doc = new PdfDocument();
doc.PageSettings.Margins.All = 0;
PdfPageBase page = null;
PdfDocument original = new PdfDocument();
original.LoadFromFile("Test.pdf");

SetDocumentTemplate(doc, PdfPageSize.A4, original.PageSettings.Margins);

foreach (PdfPageBase origianlPage in original.Pages)
{
    page = doc.Pages.Add(new SizeF(origianlPage.Size.Width, origianlPage.Size.Height));
    origianlPage.CreateTemplate().Draw(page, 0, -(original.PageSettings.Margins.Top));
}

doc.SaveToFile("output.pdf");
System.Diagnostics.Process.Start("output.pdf");

private static void SetDocumentTemplate(PdfDocument doc, SizeF pageSize, PdfMargins margin)
{
    PdfPageTemplateElement topSpace = new PdfPageTemplateElement(pageSize.Width, margin.Top);
    topSpace.Foreground = true;
    doc.Template.Top = topSpace;
    PdfTrueTypeFont font1 = new PdfTrueTypeFont(new Font("Trebuchet MS", 14f, System.Drawing.FontStyle.Italic));
    String label = "This is a PDF text header";
    SizeF size = font1.MeasureString(label);
    float y = 0;
    float x = 0;
    topSpace.Graphics.DrawString(label, font1, PdfBrushes.PaleVioletRed, x, y);
}

private void button1_Click(object sender, RoutedEventArgs e)
 {
     // Create a pdf document.
     PdfDocument doc = new PdfDocument();
     doc.PageSettings.Margins.All = 0;
     PdfPageBase page = null;
     PdfDocument original = new PdfDocument();

     original.LoadFromFile("Test.pdf");

     SetDocumentTemplate(doc, PdfPageSize.A4, original.PageSettings.Margins);
     foreach (PdfPageBase origianlPage in original.Pages)
     {
         page = doc.Pages.Add(new SizeF(origianlPage.Size.Width, origianlPage.Size.Height));
         origianlPage.CreateTemplate().Draw(page, 0, -(original.PageSettings.Margins.Top));

     }

     doc.SaveToFile("output.pdf");
     System.Diagnostics.Process.Start("output.pdf");

 }
 private static void SetDocumentTemplate(PdfDocument doc, SizeF pageSize, PdfMargins margin)
 {
     PdfPageTemplateElement topSpace = new PdfPageTemplateElement(pageSize.Width, margin.Top);
     topSpace.Foreground = true;
     doc.Template.Top = topSpace;
     PdfTrueTypeFont font1 = new PdfTrueTypeFont(new Font("Trebuchet MS", 14f, System.Drawing.FontStyle.Italic));
     String label = "This is a PDF text header";
     SizeF size = font1.MeasureString(label);
     float y = 0;
     float x = 0;
     topSpace.Graphics.DrawString(label, font1, PdfBrushes.PaleVioletRed, x, y);
 }

PdfDocument pdfDoc = new PdfDocument();
PdfPageBase page = pdfDoc.Pages.Add();

PdfGraphicsState state = page.Canvas.Save();

PdfPen pen = new PdfPen(System.Drawing.Color.ForestGreen, 0.1f);
PdfPen pen1 = new PdfPen(System.Drawing.Color.Red, 3f);
PdfBrush brush = new PdfSolidBrush(System.Drawing.Color.DeepSkyBlue);

page.Canvas.DrawRectangle(pen, new System.Drawing.Rectangle(new System.Drawing.Point(2, 22), new System.Drawing.Size(120, 120)));
page.Canvas.DrawPie(pen1, 150, 30, 100, 90, 360, 360);
page.Canvas.DrawEllipse(brush, 350, 40, 20, 60);

page.Canvas.Restore(state);

pdfDoc.SaveToFile("Shapes.pdf");

private void button1_Click(object sender, RoutedEventArgs e)
{
    PdfDocument pdfDoc = new PdfDocument();
    PdfPageBase page = pdfDoc.Pages.Add();
    PdfGraphicsState state = page.Canvas.Save();
    PdfPen pen = new PdfPen(System.Drawing.Color.ForestGreen, 0.1f);
    PdfPen pen1 = new PdfPen(System.Drawing.Color.Red, 3f);
    PdfBrush brush = new PdfSolidBrush(System.Drawing.Color.DeepSkyBlue);

    //draw rectangle
    page.Canvas.DrawRectangle(pen, new System.Drawing.Rectangle(new System.Drawing.Point(2, 22), new System.Drawing.Size(120, 120)));
    //draw circle
    page.Canvas.DrawPie(pen1, 150, 30, 100, 90, 360, 360);
    //draw ellipse
    page.Canvas.DrawEllipse(brush, 350, 40, 20, 60);
    
    page.Canvas.Restore(state);
    pdfDoc.SaveToFile("Shapes.pdf");
}