How to add text to a PDF page in C#

The shortest working example

If you want to place text onto a page with explicit font options, use the overload that accepts FontOptions.

using ZingPDF;
using ZingPDF.Graphics;
using ZingPDF.Syntax.CommonDataStructures;
using ZingPDF.Text;

using var pdf = Pdf.Create();
var page = await pdf.GetPageAsync(1);

await page.AddTextAsync(
    "Invoice paid",
    Rectangle.FromCoordinates(new Coordinate(72, 720), new Coordinate(260, 760)),
    new FontOptions
    {
        ResourceName = "Helv",
        Size = 18,
        Colour = RGBColour.Black
    });

await pdf.SaveAsync(File.Create("text-added.pdf"));

The rectangle controls where the text is laid out

The bounding box is not just a rough position marker. It is the space ZingPDF uses for layout.

If you want the text in a specific part of the page, define the rectangle for that area instead of treating it like a single point.

Pass layout options when the text may not fit

If the text could be wider than the box, decide that up front instead of relying on whatever happens at the requested size.

using ZingPDF.Text;

await page.AddTextAsync(
    "This sentence is longer than the original box width.",
    Rectangle.FromCoordinates(new Coordinate(72, 680), new Coordinate(240, 720)),
    new FontOptions
    {
        ResourceName = "Helv",
        Size = 24,
        Colour = RGBColour.Black
    },
    new TextLayoutOptions
    {
        Overflow = TextOverflowMode.ShrinkToFit
    });

Use ShrinkToFit when the text must stay inside the box, or choose a different overflow mode if clipping is the better fit for the document.

Switch to a registered font when you need one

The registered-font overload is a better fit when you want a standard font helper or an embedded TrueType font.

Register the font at the document level, then pass the returned PdfFont into AddTextAsync(...).