Nedo.AspNet.PdfEngine 1.0.3

Nedo.AspNet.PdfEngine

ASP.NET Core library for PDF manipulation — watermarking, image rasterization (anti-copy), compression, and encryption at rest.

Installation

dotnet add package Nedo.AspNet.PdfEngine

Quick Start

1. Register Services

builder.Services
    .AddPdfEngine()       // Core service
    .AddWatermark()       // Text / Stamp / Image watermark
    .AddRasterization()   // PDF → image-based pages (anti-copy)
    .AddCompression()     // FlateEncode compression
    .AddEncryption();     // AES password protection

2. Use the Service

app.MapPost("/pdf/watermark", async (IFormFile file, IPdfService pdfService) =>
{
    using var ms = new MemoryStream();
    await file.CopyToAsync(ms);

    var request = new PdfOperationBuilder()
        .WithInput(ms.ToArray())
        .AddWatermark(opt =>
        {
            opt.Text = "CONFIDENTIAL";
            opt.Opacity = 0.3;
            opt.Repeat = true;
        })
        .Build();

    var result = await pdfService.ProcessAsync(request);
    return Results.File(result.OutputPdf!, "application/pdf", "watermarked.pdf");
});

Features

1. Text Watermark

Transparent text overlaid across the page — tiled or single-positioned.

// Tiled diagonal text
.AddWatermark(opt =>
{
    opt.Text = "DRAFT";
    opt.FontSize = 72;
    opt.Opacity = 0.15;
    opt.Rotation = -45;
    opt.Color = "#FF5252";
    opt.Repeat = true;
    opt.RepeatSpacing = 150;
})

// Single positioned text (bottom-right)
.AddWatermark(opt =>
{
    opt.Text = "Confidential";
    opt.FontSize = 36;
    opt.Opacity = 0.3;
    opt.Repeat = false;
    opt.Position = WatermarkPosition.BottomRight;
    opt.Margin = 20;
})

// Fit diagonal — auto-sizes to span full page diagonal
.AddWatermark(opt =>
{
    opt.Text = "DRAFT";
    opt.FitDiagonal = true;   // auto FontSize & Rotation
    opt.Repeat = false;
    opt.Opacity = 0.15;
    opt.Color = "#FF5252";
    opt.Margin = 80;          // padding from corners
})

2. Stamp Watermark (Info-Box)

A box with background, border, and multi-line text — placed at any of 9 positions.

┌───────────┬────────────┬────────────┐
│ TopLeft   │ TopCenter  │ TopRight   │
├───────────┼────────────┼────────────┤
│CenterLeft │  Center    │CenterRight │
├───────────┼────────────┼────────────┤
│BottomLeft │BottomCenter│BottomRight │
└───────────┴────────────┴────────────┘

.AddStamp(opt =>
{
    opt.Text = "DOKUMEN TIDAK TERKENDALI\n"
             + "Diunduh dari IP Address 103.175.159.20\n"
             + "Tanggal 22-02-2026 18:21:03\n"
             + "Oleh John Doe (johndoe@gmail.com)\n"
             + "Bersifat Private";
    opt.Position = WatermarkPosition.TopCenter;
    opt.Color = "#E8356D";
    opt.BackgroundColor = "#FFF0F0";
    opt.BorderColor = "#E8356D";
    opt.FontSize = 11;
    opt.Padding = 12;
    opt.Margin = 20;
    opt.BoldFirstLine = true;
    opt.Opacity = 0.75;
})

// Simple shorthand
.AddStamp("CONFIDENTIAL\nInternal Only", WatermarkPosition.TopRight)

3. Image Watermark

Overlay a PNG/JPEG image with transparency support.

.AddImageWatermark(opt =>
{
    opt.ImageBytes = File.ReadAllBytes("logo.png");
    opt.Position = WatermarkPosition.BottomRight;
    opt.ImageScale = 0.5;       // half size
    opt.Opacity = 0.3;
    opt.Margin = 30;
})

// Simple shorthand
.AddImageWatermark(logoBytes, WatermarkPosition.Center)

4. Rasterization (Anti-Copy)

Converts each page to a flat image — text becomes non-selectable and non-copiable.

.Rasterize(opt =>
{
    opt.Dpi = 200;                           // 150 = screen, 300 = print
    opt.ImageFormat = RasterImageFormat.Png; // or Jpeg
    opt.Quality = 85;                        // JPEG quality (1–100)
})

5. Compression

Reduces PDF file size via FlateEncode and optional image re-encoding.

.Compress(opt =>
{
    opt.Level = PdfCompressionLevel.Maximum;
    opt.CompressImages = true;
    opt.ImageQuality = 75;
})

6. Encryption

Password-protect with granular permissions.

.Encrypt(opt =>
{
    opt.OwnerPassword = "admin123";     // full access
    opt.UserPassword = "viewer456";     // required to open
    opt.AllowPrint = true;
    opt.AllowCopy = false;
    opt.AllowModify = false;
    opt.AllowAnnotations = false;
})

// Simple shorthand
.Encrypt("admin-password", "viewer-password")

7. Pipeline (Chaining Operations)

Apply multiple operations in sequence:

var (input, operations) = new PdfPipelineBuilder()
    .WithInput(pdfBytes)
    .AddWatermark(opt => { opt.Text = "CONFIDENTIAL"; opt.Repeat = true; })
    .AddRasterize(opt => opt.Dpi = 200)
    .AddCompress()
    .AddEncrypt(opt => opt.OwnerPassword = "secret")
    .Build();

var result = await pdfService.ProcessPipelineAsync(input, operations);

Property Reference

WatermarkOptions

Shared Properties (All Styles)

Text-Specific Properties

Stamp-Specific Properties

Image-Specific Properties

RasterizeOptions

CompressionOptions

EncryptionOptions

Enums

WatermarkStyle

WatermarkPosition

PdfCompressionLevel

RasterImageFormat

PdfResult

Health Check

builder.Services.AddPdfEngineHealthCheck();
app.MapHealthChecks("/health");

Extending

Implement IPdfProcessor and register it:

public class MyCustomProcessor : IPdfProcessor
{
    public PdfOperationType OperationType => PdfOperationType.Watermark;

    public Task<PdfResult> ProcessAsync(PdfRequest request, CancellationToken ct)
    {
        // Custom logic
    }
}

services.AddSingleton<IPdfProcessor, MyCustomProcessor>();

Docker / Linux

The library uses PDFsharp 6 and Docnet.Core (PDFium). For Linux/Docker containers:

RUN apt-get update && apt-get install -y \
    fonts-dejavu-core \
    fontconfig \
    libgdiplus

License

MIT