//Create new text object with stock font
var to = PdfTextObject.Create();
to.Font = PdfFont.CreateStock(pdfViewer1.Document, FontStockNames.Arial);
//Set text to TextObject
to.TextUnicode = "Sample text";
//Scale text object with scale factor = 50
to.Transform(50, 0, 0, 50, 0, 0);
//Set object location in page coordinates
to.Location = new PointF(100, 100);
//Set object color
to.StrokeColor = Color.Black;
//Insert object to a page
Document.Pages[0].PageObjects.InsertObject(to);