Building a PDF Invoice in 30 Lines of C# Code with TerraPDF

Invoices are the most common PDF use case. With traditional libraries (PdfSharp, iText), you're managing coordinates, page breaks, and table layouts manually — hundreds of lines of boilerplate.

TerraPDF changes this. Its declarative, layout-first API lets you build professional invoices in 30 lines of actual generation code.

Setup

dotnet add package TerraPDF  # MIT-licensed, zero dependencies

Complete 30-Line Invoice Generator

using TerraPDF.Core;
using TerraPDF.Helpers;

public record Invoice(string Number, DateTime Date, string Customer, List<Item> Items)
{
    public decimal Subtotal => Items.Sum(i => i.LineTotal);
    public decimal Tax      => Math.Round(Subtotal * 0.10m, 2);
    public decimal Total    => Subtotal + Tax;
}
public record Item(string Description, int Quantity, decimal UnitPrice)
{
    public decimal LineTotal => Quantity * UnitPrice;
}

public static class InvoiceGenerator
{
    public static byte[] Generate(Invoice inv)
    {
        return Document.Create(doc =>
        {
            doc.Page(page =>
            {
                page.Size(PageSize.A4);
                page.Margin(2, Unit.Centimetre);
                page.DefaultTextStyle(s => s.FontSize(10));

                // ── Header ───────────────────────────────────────────────────
                page.Header().Column(h =>
                {
                    h.Item().Text("INVOICE").Bold().FontSize(22).FontColor("#1a4a8a");
                    h.Item().Row(r =>
                    {
                        r.RelativeItem().Text($"#: {inv.Number}  |  Date: {inv.Date:yyyy-MM-dd}");
                        r.AutoItem().AlignRight()
                           .Text($"Due: {inv.Date.AddDays(30):yyyy-MM-dd}")
                           .FontColor(Color.Red.Medium);
                    });
                    h.Item().LineHorizontal(1, "#1a4a8a");
                });

                // ── Content ──────────────────────────────────────────────────
                page.Content().Column(c =>
                {
                    c.Spacing(12);

                    // Bill-from / Bill-to
                    c.Item().Row(r =>
                    {
                        r.RelativeItem().Text("Your Company\n123 Main St\nCity, Country");
                        r.RelativeItem().AlignRight().Text($"BILL TO:\n{inv.Customer}");
                    });

                    // Line-items table
                    c.Item().Table(t =>
                    {
                        t.ColumnsDefinition(cols =>
                        {
                            cols.RelativeColumn(5);  // Description
                            cols.RelativeColumn(1);  // Qty
                            cols.RelativeColumn(2);  // Unit Price
                            cols.RelativeColumn(2);  // Total
                        });

                        t.HeaderRow(row =>
                        {
                            row.Cell().Background("#1a4a8a").Padding(5)
                               .Text("Description").Bold().FontColor(Color.White);
                            row.Cell().Background("#1a4a8a").Padding(5).AlignCenter()
                               .Text("Qty").Bold().FontColor(Color.White);
                            row.Cell().Background("#1a4a8a").Padding(5).AlignRight()
                               .Text("Price").Bold().FontColor(Color.White);
                            row.Cell().Background("#1a4a8a").Padding(5).AlignRight()
                               .Text("Total").Bold().FontColor(Color.White);
                        });

                        foreach (var item in inv.Items)
                        {
                            t.Row(row =>
                            {
                                row.Cell().Padding(5).Text(item.Description);
                                row.Cell().Padding(5).AlignCenter().Text(item.Quantity.ToString());
                                row.Cell().Padding(5).AlignRight().Text($"{item.UnitPrice:C}");
                                row.Cell().Padding(5).AlignRight().Text($"{item.LineTotal:C}");
                            });
                        }
                    });

                    // Totals block (right-aligned)
                    c.Item().Row(r =>
                    {
                        r.RelativeItem(7); // left spacer

                        r.RelativeItem(3).Column(tot =>
                        {
                            tot.Item().LineHorizontal(1, Color.Grey.Lighten2);
                            tot.Item().Row(tr =>
                            {
                                tr.RelativeItem().Text("Subtotal:");
                                tr.RelativeItem().AlignRight().Text($"{inv.Subtotal:C}");
                            });
                            tot.Item().Row(tr =>
                            {
                                tr.RelativeItem().Text("Tax (10%):");
                                tr.RelativeItem().AlignRight().Text($"{inv.Tax:C}");
                            });
                            tot.Item().LineHorizontal(1.5, "#1a4a8a");
                            tot.Item().Row(tr =>
                            {
                                tr.RelativeItem().Text("TOTAL DUE").Bold();
                                tr.RelativeItem().AlignRight().Text($"{inv.Total:C}").Bold()
                                   .FontColor("#1a4a8a");
                            });
                        });
                    });

                    // Payment terms
                    c.Item().MarginTop(8).Border(1, Color.Grey.Lighten2)
                      .Padding(8).Text(
                        "Payment due within 30 days. Late payments incur 1.5% monthly interest.")
                      .FontSize(9).FontColor(Color.Grey.Darken1).Justify();

                    // Thank you
                    c.Item().AlignCenter()
                      .Text("Thank you for your business!").FontSize(9).FontColor(Color.Grey.Medium);
                });

                // ── Footer ───────────────────────────────────────────────────
                page.Footer().AlignCenter().Text(t =>
                {
                    t.Span("Page "); t.CurrentPageNumber();
                    t.Span(" of "); t.TotalPages();
                });
            });
        }).PublishPdf();  // returns byte[]
    }
}

Usage:

var inv = new Invoice("INV-2025-001", DateTime.Today, "Acme Corp", new()
{
    new("Web Development", 40, 150m),
    new("Server Maintenance", 10, 100m),
});

File.WriteAllBytes("invoice.pdf", InvoiceGenerator.Generate(inv));

What you get: Header, bill-from/to, multi-line table with auto page breaks, totals, payment terms, footer with page numbers — all in 30 lines inside the Document.Create lambda.

Why This Works: Layout-First, Not Coordinate-First

Traditional PDF libraries force you to:

• ❌ Calculate Y positions manually (y -= 18)
• ❌ Check for page overflow and create new pages
• ❌ Draw table grid lines individually
• ❌ Recreate font objects repeatedly

TerraPDF handles it:

• ✅ Automatic pagination and text wrapping
• ✅ Native tables with repeating headers across pages
• ✅ Built-in page numbering (X of Y)
• ✅ Declarative containers (Column, Row) manage spacing

You describe what to render. TerraPDF handles how to position it.

Advanced: Multi-Page Tables With Auto Headers

TerraPDF tables automatically repeat header rows on page breaks — no extra code needed. 100 items? It splits across as many pages as required:

table.HeaderRow(row =>  // This repeats on every page
{
    row.Cell().Background("#1a4a8a").Text("Description").Bold();
    // ... other headers
});

foreach (var item in largeItemList)  // Automatic page breaks
    table.Row(row => { /* cells */ });

This is extremely hard in PdfSharp or DIY approaches.

Comparison: TerraPDF vs PdfSharp vs DIY for Invoices

Production Pattern: Reusable Components

For larger projects, extract into a reusable IComponent:

public class InvoiceDocument : IComponent
{
    private readonly Invoice _data;
    public InvoiceDocument(Invoice data) => _data = data;

    public void Compose(IContainer container) => container.Page(page =>
    {
        page.Header().Text($"INVOICE #{_data.Number}").Bold();
        page.Content().Table(t => BuildInvoiceTable(t));
        page.Footer().Text($"Page {page.PageNumber}");
    });

    private void BuildInvoiceTable(ITableDescriptor t) { /* table logic */ }
}

Document.Create(new InvoiceDocument(invoice)).PublishPdf("invoice.pdf");

Quick Enhancements

• Add logo: r.ConstantItem(120).Image("logo.png", 40);
• Add QR code: Generate as image, embed with .Image()
• Multi-currency: Use CultureInfo for formatting
• Conditional sections: Use .ShowIf(condition) decorator

Best Practices

1. Use records for data models (concise, immutable)
2. Centralize constants (colors, sizes) to const fields
3. Extract table building to separate methods
4. Validate input before generation
5. Reuse styles with page.DefaultTextStyle() instead of repeating on every call
6. Unit test by parsing PDF text with a PDF library

Why This Matters

TerraPDF makes PDF generation approachable. No coordinate math. No manual page breaks. No grid-drawing loops.

In 30 lines you get:

• Professional multi-page invoices
• Auto-pagination with repeating table headers
• Built-in page numbers
• Clean, maintainable code
• MIT license

If you've avoided PDF generation, TerraPDF changes the game.