Stamping & Watermarks

Apply text stamps, image stamps, and watermarks to every page of a PDF. FolioPDF generates each stamp as a transparent overlay using its layout engine, then composites it via the native qpdf pipeline — so stamps support the full typography and image codec capabilities of the library.

Text Stamps

Use StampText to place a text label on every page. The stamp is positioned according to its alignment and margin settings:

PdfEditor.Open("report.pdf")
    .StampText(new TextStamp("CONFIDENTIAL")
    {
        FontSize = 48,
        Color = Color.FromHex("#CC0000"),
        Opacity = 0.3f,
        Rotation = -45,
        HorizontalAlignment = StampAlignment.Center,
        VerticalAlignment = StampAlignment.Center
    })
    .Save("report-stamped.pdf");

TextStamp Properties

StampAlignment Enum

Image Stamps

Use StampImage to place a logo, badge, or other image on every page:

PdfEditor.Open("report.pdf")
    .StampImage(new ImageStamp("company-logo.png")
    {
        Width = 120,
        Height = 40,
        HorizontalAlignment = StampAlignment.End,
        VerticalAlignment = StampAlignment.Start,
        Margin = 30
    })
    .Save("report-branded.pdf");

Creating from Bytes

When the image is already in memory (e.g. from a database or API), pass the byte array directly:

byte[] logo = await httpClient.GetByteArrayAsync(logoUrl);

PdfEditor.Open("proposal.pdf")
    .StampImage(new ImageStamp(logo)
    {
        Width = 100,
        Height = 100,
        HorizontalAlignment = StampAlignment.Center,
        VerticalAlignment = StampAlignment.Center
    })
    .Save("proposal-stamped.pdf");

ImageStamp Properties

Watermark Patterns

Diagonal "DRAFT" Watermark

The classic diagonal watermark uses large, semi-transparent text rotated at -45 degrees:

PdfEditor.Open("proposal.pdf")
    .StampText(new TextStamp("DRAFT")
    {
        FontSize = 72,
        Color = Color.FromRgb(200, 200, 200),
        Opacity = 0.25f,
        Rotation = -45,
        Bold = true,
        HorizontalAlignment = StampAlignment.Center,
        VerticalAlignment = StampAlignment.Center
    })
    .Save("proposal-draft.pdf");

Diagonal "CONFIDENTIAL" Watermark in Red

PdfEditor.Open("financials.pdf")
    .StampText(new TextStamp("CONFIDENTIAL")
    {
        FontSize = 60,
        Color = Color.FromHex("#FF0000"),
        Opacity = 0.15f,
        Rotation = -45,
        Bold = true,
        HorizontalAlignment = StampAlignment.Center,
        VerticalAlignment = StampAlignment.Center
    })
    .Save("financials-confidential.pdf");

Corner Logo Branding

Place a company logo in the top-right corner of every page:

PdfEditor.Open("whitepaper.pdf")
    .StampImage(new ImageStamp("brand-logo.png")
    {
        Width = 80,
        Height = 30,
        HorizontalAlignment = StampAlignment.End,
        VerticalAlignment = StampAlignment.Start,
        Margin = 25
    })
    .Save("whitepaper-branded.pdf");

Bottom-Left Date Stamp

var dateText = $"Printed: {DateTime.Now:yyyy-MM-dd HH:mm}";

PdfEditor.Open("report.pdf")
    .StampText(new TextStamp(dateText)
    {
        FontSize = 9,
        Color = Color.FromRgb(128, 128, 128),
        Opacity = 1.0f,
        HorizontalAlignment = StampAlignment.Start,
        VerticalAlignment = StampAlignment.End,
        Margin = 30
    })
    .Save("report-dated.pdf");

Centred "VOID" Stamp

PdfEditor.Open("cancelled-invoice.pdf")
    .StampText(new TextStamp("VOID")
    {
        FontSize = 96,
        Color = Color.FromHex("#CC0000"),
        Opacity = 0.4f,
        Bold = true,
        HorizontalAlignment = StampAlignment.Center,
        VerticalAlignment = StampAlignment.Center
    })
    .Save("invoice-voided.pdf");

Background Watermark (Behind Content)

Set BehindContent = true to place the stamp underneath existing page content. This is useful for light background patterns that should not obscure text:

PdfEditor.Open("form.pdf")
    .StampText(new TextStamp("SAMPLE")
    {
        FontSize = 100,
        Color = Color.FromRgb(230, 230, 230),
        Opacity = 0.5f,
        Rotation = -45,
        Bold = true,
        BehindContent = true,
        HorizontalAlignment = StampAlignment.Center,
        VerticalAlignment = StampAlignment.Center
    })
    .Save("form-sample.pdf");

Combining Stamps

Chain multiple stamps in a single editor session. Each stamp is applied sequentially:

PdfEditor.Open("contract.pdf")
    // Logo in top-right corner
    .StampImage(new ImageStamp("logo.png")
    {
        Width = 100,
        Height = 35,
        HorizontalAlignment = StampAlignment.End,
        VerticalAlignment = StampAlignment.Start,
        Margin = 25
    })
    // Date in bottom-left
    .StampText(new TextStamp($"Generated: {DateTime.Now:yyyy-MM-dd}")
    {
        FontSize = 8,
        Color = Color.FromRgb(100, 100, 100),
        Opacity = 1.0f,
        HorizontalAlignment = StampAlignment.Start,
        VerticalAlignment = StampAlignment.End,
        Margin = 25
    })
    // Diagonal watermark
    .StampText(new TextStamp("DRAFT")
    {
        FontSize = 72,
        Opacity = 0.15f,
        Rotation = -45,
        Bold = true,
        Color = Color.FromRgb(200, 200, 200)
    })
    .Save("contract-marked.pdf");

Static API

For one-off stamping without a full editor chain, use the static PdfStamper methods directly:

// File-to-file
PdfStamper.StampText("input.pdf", "output.pdf", new TextStamp("APPROVED")
{
    FontSize = 36,
    Color = Color.FromHex("#008000"),
    Opacity = 0.5f,
    HorizontalAlignment = StampAlignment.End,
    VerticalAlignment = StampAlignment.End,
    Margin = 40
});

// In-memory
byte[] pdfBytes = File.ReadAllBytes("input.pdf");
byte[] stamped = PdfStamper.StampText(pdfBytes, new TextStamp("COPY"));
File.WriteAllBytes("output.pdf", stamped);

// Image stamp, file-to-file
PdfStamper.StampImage("input.pdf", "output.pdf",
    new ImageStamp("logo.png") { Width = 80, Height = 30 });

How Stamping Works Internally

Understanding the internals helps when troubleshooting sizing or alignment issues:

1. FolioPDF reads the first page's dimensions from the target PDF.
2. A transparent single-page PDF is generated using the layout engine with the same page size, containing just the stamp content at the requested position.
3. The overlay (or underlay, if BehindContent = true) is applied to every page of the target document via qpdf's overlay/underlay pipeline.
4. The result is a new PDF with the stamp composited onto every page.

Next Steps

• Drawing on Pages — draw text, lines, and rectangles directly onto page content
• Merge, Split & Overlay — qpdf-level overlay and underlay with full page mapping
• Page Manipulation — rotation, cropping, and page boxes