Edit PDF in C#

using var presentation = new Presentation();
presentation.Slides.RemoveAt(0);
presentation.Slides.AddFromPdf("document.pdf");

var slide = presentation.Slides[0];

if (slide.Shapes[0] is IAutoShape shape && shape.TextFrame is not null)
{
    shape.TextFrame.Text = "New text";
}

presentation.Save("document.pdf", SaveFormat.Pdf);