Issue when adding Signature to the file

I am facing a strange  issue when  trying to add Visual signature field to existed PDF file. Existed PDF file (created with the QuickPDF.DLL) has 3 pages with 2 Form fields on each page, lets name it Field_1 and Field_2. So, pages 1,2, and 3  have identical value in those fields - Field_1 and Field_2.

There is no issues at this stage, I can open PDF file, modify the value of those fields, and save it. Further I try to add Visual digital signature follow exact this instructions I found in this Forum’s thread http://www.quickpdf.org/forum/topic2563&OB=ASC.html (see Rowan’s message):

      SignProcessID := DPL.NewSignProcessFromFile('TheUnsignedFile.pdf', '');

      if (SignProcessID > 0) then

      begin

        DPL.SetSignProcessPFXFromFile(SignProcessID, 'qpl_test.pfx', 'testing');

        DPL.SetSignProcessInfo(SignProcessID, 'To test digital signatures', 'The World', 'Contact me');

        DPL.SetSignProcessField(SignProcessID, 'Contract Signature');

        DPL.SetSignProcessFieldBounds(SignProcessID, 100, 600, 200, 100);

        DPL.SetSignProcessFieldImageFromFile(SignProcessID, 'visualsignature.jpg', 0);

        DPL.EndSignProcessToFile(SignProcessID, 'TheSignedFile.pdf');

      end;

Here is the issue: Resulting PDF file has a Visual Digital signature on the first page, but missing Field_1 and Field_2 on pages 2 and 3.

I noticed that DPL.EndSignProcessToFile() returns 0, and I have a filling I am missing something or doing something wrong. Any thoughts?  

Thanks

Marat