---
title: "Add a watermark to a PDF in C#"
url: https://recursiveai.org/onepdf/cookbook/add-watermark/
description: "Add a text or image watermark to every page of a PDF in C#: rotated, semi-transparent, over or under the content. Runnable code, with OnePDF."
version: "1.15.0"
---

# Add a watermark to a PDF in C#

Open the PDF with editing allowed, call `AddTextStamp` and save. The program below stamps a diagonal “DRAFT” on every page of the IRS Form W-9, a public PDF you can download to try it.

```shell
dotnet new console -o Watermark && cd Watermark
dotnet add package RecursiveAI.OnePdf --version 1.15.0
curl -LO https://www.irs.gov/pub/irs-pdf/fw9.pdf
```

Put this in `Program.cs` and run `dotnet run`:

```csharp
using OnePdf;

using PdfDocument doc = PdfDocument.Open("fw9.pdf",
    new PdfOpenOptions { AllowEditing = true });

// "DRAFT" across every page: 45 degrees, red, 15% opaque, centered on each page.
PdfCreatedFont font = doc.AddStandardFont("Helvetica-Bold");
doc.AddTextStamp("DRAFT", font, 120, new PdfStampOptions
{
    Opacity = 0.15,
    RotationDegrees = 45,
    Color = (0.7, 0.1, 0.1),
});

doc.Save("fw9-draft.pdf");
Console.WriteLine($"Watermarked {doc.PageCount} pages: fw9-draft.pdf");
```

```text
Watermarked 6 pages: fw9-draft.pdf
```

Each of the six pages now shows “DRAFT” in light red across its middle, over the text. The stamp is drawn once into a shared form and placed on every page, so it is stored once however many pages show it. The pages’ own content is left exactly as it was.

## An image watermark, behind the content

To use a logo instead, add the image to the document and stamp it. `Underlay` puts it under the page’s text, so the form stays readable:

```shell
curl -o logo.png https://recursiveai.org/assets/brand/icon-512.png
```

```csharp
using OnePdf;

using PdfDocument doc = PdfDocument.Open("fw9.pdf",
    new PdfOpenOptions { AllowEditing = true });

// transparency is kept
PdfCreatedImage logo = doc.AddPngImage(File.ReadAllBytes("logo.png"));
doc.AddImageStamp(logo, 300, 300, new PdfStampOptions   // 300 x 300 points
{
    Opacity = 0.1,
    Placement = PdfContentPlacement.Underlay,   // under the page's content
}, pageIndexes: [0]);   // page 1 only; leave out for all pages

doc.Save("fw9-logo.pdf");
Console.WriteLine("Saved fw9-logo.pdf");
```

```text
Saved fw9-logo.pdf
```

## Options

`PdfStampOptions` sets `Opacity` (0 to 1), `RotationDegrees` (counterclockwise), `Color` (RGB, 0 to 1), `Placement` (`Overlay`, the default, or `Underlay`), a `BlendMode`, and `CenterX` and `CenterY` to move the stamp off the page center. Sizes and positions are in points, 72 to the inch. Stamps stay upright on pages that are rotated.

## Limits

- **A watermark can be removed.** It is ordinary page content: a PDF editor can delete it, and text extraction returns “DRAFT” with the rest of the text. To take information out of a file, [redact](https://recursiveai.org/onepdf/cookbook/redact/) it.
- **Standard fonts aren’t embedded.** Helvetica is supplied by the viewer, which keeps the file small but rules out PDF/A. Embed your own TrueType or OpenType font with `doc.AddFont(File.ReadAllBytes("font.ttf"))` instead.
- **Stamp before you sign.** Stamping a signed PDF changes its pages, and [signature verification](https://recursiveai.org/onepdf/cookbook/sign-and-verify/) reports the change.
- **JPEG and PNG only.** `AddJpegImage` embeds a JPEG as it is and `AddPngImage` keeps a PNG’s transparency. Convert other formats first.

To place an image at an exact spot on one page, see [Add an image to a PDF](https://recursiveai.org/onepdf/cookbook/add-image-to-pdf/). Every drawing call is in [Content creation](https://recursiveai.org/onepdf/docs/content-creation/).