Can you post the relevant pdf/fdf files ?

No Need :) Anyway, the part that fills in the PDF from FDF works without any problems. But I finally managed to get this one working. In case anyone else winds up needing to do this, here is the code that works:

FdfReader fdfReader = new FdfReader("c:\\apps5\\nexus\\Omaha_IAF.fdf");
PdfReader pdfReader = new PdfReader("c:\\apps5\\nexus\\Omaha_IAF.pdf");

PdfStamper stamper = new PdfStamper(pdfReader, new FileStream("c:\\apps5\\nexus\\Omaha_IAF_Test.pdf", FileMode.Create), '\0', true);
stamper.AcroFields.SetFields(fdfReader);
AcroFields Form = stamper.AcroFields;
PushbuttonField Cmd = Form.GetNewPushbuttonFromField("cmdSignature");
Cmd.Layout = PushbuttonField.LAYOUT_ICON_ONLY;
Cmd.ProportionalIcon = true;
Cmd.BorderWidth = 0;
Cmd.Visibility = BaseField.VISIBLE;
Cmd.Image = iTextSharp.text.Image.GetInstance("e:\\marcia\\AkSig.tif");
Boolean Success = Form.ReplacePushbuttonField("cmdSignature", Cmd.Field);
Form.RenameField("cmdSignature", "cmdActualSignature");
stamper.Close();

axAcroPDF1.LoadFile("c:\\apps5\\nexus\\Omaha_IAF_Test.pdf");
axAcroPDF1.setShowToolbar(true);

Update: Oh, Major WAAAAHHHH! I got this working in Visual Studio but I still can't get it working properly in VFP :(