How to Add Watermarks to PDFs in C# Using IronPDF

using IronPdf;

// This code demonstrates how to create a PDF document and apply a watermark to it using IronPdf library.

// Define the HTML content for the watermark. The HTML can include both text and image elements.
string watermarkHtml = @"
<img src='https://ironsoftware.com/img/products/ironpdf-logo-text-dotnet.svg' alt='IronPDF Logo'>
<h1>Iron Software</h1>";

// Create an instance of ChromePdfRenderer, which allows rendering PDFs from HTML content.
ChromePdfRenderer renderer = new ChromePdfRenderer();

// Render a simple PDF document containing an H1 header with the word "Watermark".
PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Watermark</h1>");

// Apply the watermark to the entire PDF document. The watermarkHtml will be overlaid on each page of the PDF.
pdf.WatermarkAllPages(new IronPdf.PdfDocumentOptions.HtmlStamp() {
    Html = watermarkHtml,
    Opacity = 100, // Set the opacity level of the watermark where 100 is fully visible
    HorizontalAlignment = IronPdf.Rendering.HtmlWatermarkOptions.HorizontalAlign.Center,
    VerticalAlignment = IronPdf.Rendering.HtmlWatermarkOptions.VerticalAlign.Middle
});

// Save the watermarked PDF document to a file named "watermark.pdf".
pdf.SaveAs("watermark.pdf");

// Import necessary namespaces from IronPdf and its editing utilities
using IronPdf;
using IronPdf.Editing;

// Define the HTML content to be used as a watermark
string watermarkHtml = @"
<img style='width: 200px;' src='https://ironsoftware.com/img/products/ironpdf-logo-text-dotnet.svg'>
<h1>Iron Software</h1>";

// Create a new instance of ChromePdfRenderer which will be used to render HTML into PDF
ChromePdfRenderer renderer = new ChromePdfRenderer();

// Render a simple HTML content as PDF for adding watermark later
PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Watermark</h1>");

// TextWatermarkOptions is meant for text; for HTML watermarks, we will use HtmlStampOptions.
// Correct usage involves creating an instance of HtmlStampOptions and then applying it.
HtmlStampOptions htmlStampOptions = new HtmlStampOptions
{
    Rotation = 45, // Rotate the watermark by 45 degrees
    Opacity = 70   // Set watermark opacity to 70%
};

// Apply a watermark to the PDF document with specified HTML.
// The watermark will be rotated by 45 degrees and have an opacity of 0.7 (70%).
pdf.ApplyStamp(watermarkHtml, htmlStampOptions);

// Save the watermarked PDF to a file
pdf.SaveAs("watermarkOpacityAndRotation.pdf");

using IronPdf;
using IronPdf.Editing;

// Define HTML content to be used as a watermark. This includes an image and header text.
string watermarkHtml = @"
<img style='width: 200px;' src='https://ironsoftware.com/img/products/ironpdf-logo-text-dotnet.svg'>
<h1>Iron Software</h1>";

// Create an instance of ChromePdfRenderer to render HTML content as PDF.
ChromePdfRenderer renderer = new ChromePdfRenderer();

// Render a simple HTML snippet into a PDF document.
PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Watermark</h1>");

// Apply the defined watermark to the document. It is positioned at the top-right corner of each page.
// '50' represents the opacity level, where 100 is fully opaque and 0 is fully transparent.
// Note: Ensure that the watermark method provided supports these parameters.
pdf.WatermarkHTML(watermarkHtml, opacity: 50, verticalAlignment: VerticalAlignment.Top, horizontalAlignment: HorizontalAlignment.Right);

// Save the resulting PDF document with the watermark to a file named "watermarkLocation.pdf".
pdf.SaveAs("watermarkLocation.pdf");