C#/VB.NET: Add, Hide or Delete Layers in PDF

PDF layer is a feature that arranges the content of a PDF file in layers, which allows users to selectively set some content to be visible and others to be invisible in the same PDF file. PDF layers are a common element used in layered artwork, maps and CAD drawings. This article will demonstrate how to programmatically add, hide or delete layers in a PDF file using Spire.PDF for .NET.

Install Spire.PDF for .NET

To begin with, you need to add the DLL files included in the Spire.PDF for.NET package as references in your .NET project. The DLLs files can be either downloaded from this link or installed via NuGet.

PM> Install-Package Spire.PDF

Add Layers to a PDF Document in C# and VB.NET

Spire.PDF for .NET provides PdfDocument.Layers.AddLayer() method to add a layer in a PDF document, and you can then draw text, lines, images or shapes on the PDF layer. The detailed steps are as follows.

  • Create a PdfDocument instance.
  • Load a sample PDF file using PdfDocument.LoadFromFile() method.
  • Add a layer with specified name in the PDF using PdfDocument.Layers.AddLayer(String) method. Or you can also set the visibility of the layer while adding it using PdfDocument.Layers.AddLayer(String, PdfVisibility) method.
  • Create a canvas for the layer using PdfLayer.CreateGraphics() method.
  • Draw text, image or other elements on the canvas.
  • Save the result document using PdfDocument.SaveToFile() method.
  • C#
  • VB.NET
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)));
            }
        }
    }
} 

C#/VB.NET: Add, Hide or Delete Layers in PDF

Set Visibility of Layers in a PDF Document in C# and VB.NET

To set the visibility of an existing layer, you'll need to get a specified layer by its index or name using PdfDocument.Layers property, and then show or hide the layer using PdfLayer.Visibility property. The detailed steps are as follows.

  • Create a PdfDocument instance.
  • Load a sample PDF document using PdfDocument.LoadFromFile() method.
  • Set the visibility of a specified layer using PdfDocument.Layers.Visibility property.
  • Save the result document using PdfDocument.SaveToFile() method.
  • C#
  • VB.NET
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");
        }
    }
}

C#/VB.NET: Add, Hide or Delete Layers in PDF

Delete Layers in a PDF Document in C# and VB.NET

Spire.PDF for .NET also allows you to remove an existing layer by its name using PdfDocument.Layers.RemoveLayer(String) method. But kindly note that the names of PDF layers may not be unique and this method will remove all PDF layers with the same name. The detailed steps are as follows.

  • Create a PdfDocument instance.
  • Load a sample PDF document using PdfDocument.LoadFromFile() method.
  • Delete a specified layer by its name using PdfDocument.Layers.RemoveLayer(String) method.
  • Save the result document using PdfDocument.SaveToFile() method.
  • C#
  • VB.NET
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);
        }
    }
}

C#/VB.NET: Add, Hide or Delete Layers in PDF

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