How to fill data in the pdf file by using FillField method?

I want to fill the field in the above pdf file by using code. The following is my code :

Aspose.Pdf.Facades.Form form = new Aspose.Pdf.Facades.Form("RZSQ.pdf","RZSQ11.pdf");

            string[] fieldNames = form.FieldNames;

            form.FillField(fieldNames[0], "123");

            form.FillField(fieldNames[1],"234");

            form.FillField(fieldNames[2], "123");

            form.FillField(fieldNames[3], "234");

            form.FillField(fieldNames[4], "123");

            form.FillField(fieldNames[5], "234");

            form.FillField(fieldNames[6], "123");

            form.FillField(fieldNames[7], "234");

            form.Save();

But it doesn’t show the filled data . Could you tell me why? Thank you very much!