PM> Install-Package Spire.PDF

using Spire.Pdf;
using Spire.Pdf.Graphics;
using Spire.Pdf.Graphics.Layer;
using System.Drawing;

namespace AddLayersToPdf
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a PdfDocument instance and load a sample PDF file
            PdfDocument pdf = new PdfDocument();
            pdf.LoadFromFile(@"C:\Users\Administrator\Desktop\Sample.pdf");

            //Invoke AddLayerWatermark method to add a watermark layer
            AddLayerWatermark(pdf);

            //Invoke AddLayerHeader method to add a header layer
            AddLayerHeader(pdf);

            //Save to file
            pdf.SaveToFile("AddLayers.pdf");
            pdf.Close();
        }

        private static void AddLayerWatermark(PdfDocument doc)
        {
            //Create a layer named "Watermark"
            PdfLayer layer = doc.Layers.AddLayer("Watermark");

            //Create a font
            PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Arial", 48), true);

            //Specify the watermark text
            string watermarkText = "CONFIDENTIAL";

            //Get text size
            SizeF fontSize = font.MeasureString(watermarkText);

            //Calculate two offsets
            float offset1 = (float)(fontSize.Width * System.Math.Sqrt(2) / 4);
            float offset2 = (float)(fontSize.Height * System.Math.Sqrt(2) / 4);

            //Get page count
            int pageCount = doc.Pages.Count;

            //Declare two variables
            PdfPageBase page;
            PdfCanvas canvas;

            //Loop through the pages
            for (int i = 0; (i < pageCount); i++)
            {
                page = doc.Pages[i];

                //Create a canvas from layer
                canvas = layer.CreateGraphics(page.Canvas);
                canvas.TranslateTransform(page.Canvas.Size.Width / 2 - offset1 - offset2, page.Canvas.Size.Height / 2 + offset1 - offset2);
                canvas.SetTransparency(0.4f);
                canvas.RotateTransform(-45);

                //Draw sting on the canvas of layer
                canvas.DrawString(watermarkText, font, PdfBrushes.DarkBlue, 0, 0);
            }
        }
        private static void AddLayerHeader(PdfDocument doc)
        {
            // Create a layer named "Header"
            PdfLayer layer = doc.Layers.AddLayer("Header");

            //Get page size
            SizeF size = doc.Pages[0].Size;

            //Specify the initial values of X and y
            float x = 90;
            float y = 40;

            //Get page count
            int pageCount = doc.Pages.Count;

            //Declare two variables
            PdfPageBase page;
            PdfCanvas canvas;

            //Loop through the pages
            for (int i = 0; (i < pageCount); i++)
            {
                //Draw an image on the layer
                PdfImage pdfImage = PdfImage.FromFile(@"C:\Users\Administrator\Desktop\img.jpg");
                float width = pdfImage.Width;
                float height = pdfImage.Height;
                page = doc.Pages[i];
                canvas = layer.CreateGraphics(page.Canvas);
                canvas.DrawImage(pdfImage, x, y, width, height);

                //Draw a line on the layer
                PdfPen pen = new PdfPen(PdfBrushes.DarkGray, 2);
                canvas.DrawLine(pen, x, (y + (height + 5)), (size.Width - x), (y + (height + 2)));
            }
        }
    }
} 

Imports Spire.Pdf
Imports Spire.Pdf.Graphics
Imports Spire.Pdf.Graphics.Layer
Imports System.Drawing

Namespace AddLayersToPdf
    Class Program
        Private Shared Sub Main(ByVal args() As String)

            'Create a PdfDocument instance and load a sample PDF file
            Dim pdf As PdfDocument = New PdfDocument
            pdf.LoadFromFile("C:\Users\Administrator\Desktop\Sample.pdf")

            'Invoke AddLayerWatermark method to add a watermark layer
            Program.AddLayerWatermark(pdf)

            'Invoke AddLayerHeader method to add a header layer
            Program.AddLayerHeader(pdf)

            'Save to file
            pdf.SaveToFile("AddLayers.pdf")
            pdf.Close()
        End Sub

        Private Shared Sub AddLayerWatermark(ByVal doc As PdfDocument)

            'Create a layer named "Watermark"
            Dim layer As PdfLayer = doc.Layers.AddLayer("Watermark")

            'Create a font
            Dim font As PdfTrueTypeFont = New PdfTrueTypeFont(New Font("Arial", 48), True)

            'Specify the watermark text
            Dim watermarkText As String = "CONFIDENTIAL"

            'Get text size
            Dim fontSize As SizeF = font.MeasureString(watermarkText)

            'Calculate two offsets
            Dim offset1 As Single = CSng((fontSize.Width * System.Math.Sqrt(2) / 4))
            Dim offset2 As Single = CSng((fontSize.Height * System.Math.Sqrt(2) / 4))

            'Get page count
            Dim pageCount As Integer = doc.Pages.Count

            'Declare two variables
            Dim page As PdfPageBase
            Dim canvas As PdfCanvas

            'Loop through the pages
            Dim i As Integer = 0
            While (i < pageCount)
                page = doc.Pages(i)

                'Create a canvas from layer
                canvas = layer.CreateGraphics(page.Canvas)
                canvas.TranslateTransform(page.Canvas.Size.Width / 2 - offset1 - offset2, page.Canvas.Size.Height / 2 + offset1 - offset2)
                canvas.SetTransparency(0.4F)
                canvas.RotateTransform(-45)

                'Draw sting on the canvas of layer
                canvas.DrawString(watermarkText, font, PdfBrushes.DarkBlue, 0, 0)
                i = (i + 1)
                i += 1
            End While
        End Sub

        Private Shared Sub AddLayerHeader(ByVal doc As PdfDocument)

            ' Create a layer named "Header"
            Dim layer As PdfLayer = doc.Layers.AddLayer("Header")

            'Get page size
            Dim size As SizeF = doc.Pages(0).Size

            'Specify the initial values of X and y
            Dim x As Single = 90
            Dim y As Single = 40

            'Get page count
            Dim pageCount As Integer = doc.Pages.Count

            'Declare two variables
            Dim page As PdfPageBase
            Dim canvas As PdfCanvas

            'Loop through the pages
            Dim i As Integer = 0
            While (i < pageCount)

                'Draw an image on the layer
                Dim pdfImage As PdfImage = PdfImage.FromFile("C:\Users\Administrator\Desktop\img.jpg")
                Dim width As Single = pdfImage.Width
                Dim height As Single = pdfImage.Height
                page = doc.Pages(i)
                canvas = layer.CreateGraphics(page.Canvas)
                canvas.DrawImage(pdfImage, x, y, width, height)

                'Draw a line on the layer
                Dim pen As PdfPen = New PdfPen(PdfBrushes.DarkGray, 2)
                canvas.DrawLine(pen, x, (y + (height + 5)), (size.Width - x), (y + (height + 2)))
                i += 1
            End While
        End Sub
    End Class
End Namespace

using Spire.Pdf;
using Spire.Pdf.Graphics.Layer;

namespace HideLayer
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a PdfDocument instance
            PdfDocument pdf = new PdfDocument();

            //Load a sample PDF document
            pdf.LoadFromFile("AddLayers.pdf");

            //Hide a specified layer by index
            pdf.Layers[0].Visibility = PdfVisibility.Off;

            //Hide a specified layer by name
            //pdf.Layers["Watermark"].Visibility = PdfVisibility.Off;

            //Save the result document
            pdf.SaveToFile("HideLayer.pdf");
        }
    }
}

Imports Spire.Pdf
Imports Spire.Pdf.Graphics.Layer

Namespace HideLayer
    Class Program
        Private Shared Sub Main(ByVal args() As String)

            'Create a PdfDocument instance
            Dim pdf As PdfDocument = New PdfDocument

            'Load a sample PDF document
            pdf.LoadFromFile("AddLayers.pdf")

            'Hide a specified layer by index
            pdf.Layers(0).Visibility = PdfVisibility.Off

            'Hide a specified layer by name
            'pdf.Layers["Watermark"].Visibility = PdfVisibility.Off;

            'Save the result document
            pdf.SaveToFile("HideLayer.pdf")
        End Sub
    End Class
End Namespace

using Spire.Pdf;

namespace DeleteLayer
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a PdfDocument instance
            PdfDocument pdf = new PdfDocument();

            //Load a sample PDF document
            pdf.LoadFromFile("AddLayers.pdf");

            //Remove a layer by name
            pdf.Layers.RemoveLayer(("Watermark"));

            //Save the result document
            pdf.SaveToFile("DeleteLayer.pdf", FileFormat.PDF);
        }
    }
}

Imports Spire.Pdf

Namespace DeleteLayer
    Class Program
        Private Shared Sub Main(ByVal args() As String)
            'Create a PdfDocument instance
            Dim pdf As PdfDocument = New PdfDocument

            'Load a sample PDF document
            pdf.LoadFromFile("AddLayers.pdf")

            'Remove a layer by name
            pdf.Layers.RemoveLayer("Watermark")

            'Save the result document
            pdf.SaveToFile("DeleteLayer.pdf", FileFormat.PDF)
        End Sub
    End Class
End Namespace

PM> Install-Package Spire.XLS

using Spire.Xls;

namespace ConvertCsvToPdf
{
    class Program
    {
        static void Main(string[] args)
        {
            //Create a Workbook instance
            Workbook wb = new Workbook();
            //Load a CSV file
            wb.LoadFromFile("Sample.csv", ",");

            //Set SheetFitToPage property as true to ensure the worksheet is converted to 1 PDF page
            wb.ConverterSetting.SheetFitToPage = true;

            //Get the first worksheet
            Worksheet sheet = wb.Worksheets[0];

            //Loop through the columns in the worksheet
            for (int i = 1; i < sheet.Columns.Length; i++)
            {
                //AutoFit columns
                sheet.AutoFitColumn(i);
            }

            //Save the worksheet to PDF
            sheet.SaveToPdf("toPDF.pdf");
        }
    }
}

Imports Spire.Xls

Namespace ConvertCsvToPdf
    Friend Class Program
        Private Shared Sub Main(ByVal args As String())
            'Create a Workbook instance
            Dim wb As Workbook = New Workbook()
            'Load a CSV file
            wb.LoadFromFile("Sample.csv", ",")

            'Set SheetFitToPage property as true to ensure the worksheet is converted to 1 PDF page
            wb.ConverterSetting.SheetFitToPage = True

            'Get the first worksheet
            Dim sheet As Worksheet = wb.Worksheets(0)

            'Loop through the columns in the worksheet
            For i As Integer = 1 To sheet.Columns.Length - 1
                'AutoFit columns
                sheet.AutoFitColumn(i)
            Next

            'Save the worksheet to PDF
            sheet.SaveToPdf("toPDF.pdf")
        End Sub
    End Class
End Namespace