Is XFA the only way? Here's a snippet of my code:
(form.Fields["f1_1"] as PdfLoadedTextBoxField).Text = sFullName;
(form.Fields["f1_5"] as PdfLoadedTextBoxField).Text = sFullName + ", " + sStreetAddr + ", " + sCity + ", " + sState + ", " + sZip;
(form.Fields["c1_6"] as PdfLoadedCheckBoxField).Checked = true;
(form.Fields["c1_1[0]"] as PdfLoadedCheckBoxField).Checked = true;
//This is where I want to load the date field
(form.Fields["Date1"] as PdfLoaded).Text = DateTime.Today.ToShortDateString();