C#/VB.NET: PDF에 배경색 또는 배경 이미지 추가

PM> Install-Package Spire.PDF 

using Spire.Pdf;
    using System.Drawing;
    
    namespace PDFBackgroundColor
    {
        class Program
        {
            static void Main(string[] args)
            {
                //Create a PdfDocument instance
                PdfDocument pdf = new PdfDocument();
    
                //Load a sample PDF file from disk
                pdf.LoadFromFile("input.pdf");
    
                //Loop through the pages in the PDF file
                foreach (PdfPageBase page in pdf.Pages)
                {
                    //Set the background color for each page
                    page.BackgroundColor = Color.Yellow;
    
                    //Set the opacity of the background
                    page.BackgroudOpacity = 0.1f;
                }
    
                //Save the result PDF file
                pdf.SaveToFile("BackgroundColor.pdf");
                pdf.Close();
    
            }
        }
    }

Imports Spire.PDF
    Imports System.Drawing
    
    Namespace PDFBackgroundColor
        Class Program
            Private Shared Sub Main(ByVal args() As String)
    
                'Create a PdfDocument instance
                Dim pdf As PdfDocument = New PdfDocument
    
                'Load a sample PDF file from disk
                pdf.LoadFromFile("input.pdf")
    
                'Loop through the pages in the PDF file
                For Each page As PdfPageBase In pdf.Pages
    
                    'Set the background color for each page
                    page.BackgroundColor = Color.Yellow
    
                    'Set the opacity of the background
                    page.BackgroudOpacity = 0.1!
                Next
    
                'Save the result PDF file
                pdf.SaveToFile("BackgroundColor.pdf")
                pdf.Close()
            End Sub
        End Class
    End Namespace

using Spire.Pdf;
    using System.Drawing;
    
    namespace PDFBackgroundImage
    {
        class Program
        {
            static void Main(string[] args)
            {
                //Create a PdfDocument instance
                PdfDocument pdf = new PdfDocument();
    
                //Load a sample PDF file from disk
                pdf.LoadFromFile("input.pdf");
    
                //Load an image
                Image background = Image.FromFile("background.png");
    
                //Loop through the pages in the PDF file
                foreach (PdfPageBase page in pdf.Pages)
                {
                    //Set the loaded image as the background image for each page
                    page.BackgroundImage = background;
    
                    //Set the opacity of the background
                    page.BackgroudOpacity = 0.2f;
                }
    
                //Save the result PDF file
                pdf.SaveToFile("BackgroundImage.pdf");
                pdf.Close();
    
            }
        }
    }

Imports Spire.PDF
    Imports System.Drawing
    
    Namespace PDFBackgroundImage
        Class Program
            Private Shared Sub Main(ByVal args() As String)
    
                'Create a PdfDocument instance
                Dim pdf As PdfDocument = New PdfDocument
    
                'Load a sample PDF file from disk
                pdf.LoadFromFile("input.pdf")
    
                'Load an image
                Dim background As Image = Image.FromFile("background.png")
    
                'Loop through the pages in the PDF file
                For Each page As PdfPageBase In pdf.Pages
    
                    'Set the loaded image as the background image for each page
                    page.BackgroundImage = background
    
                    'Set the opacity of the background
                    page.BackgroudOpacity = 0.2!
                Next
    
                'Save the result PDF file
                pdf.SaveToFile("BackgroundImage.pdf")
                pdf.Close()
            End Sub
        End Class
    End Namespace