I concatenate the two files as follows:
PdfFileEditor pdfEditor2 = new PdfFileEditor();
pdfEditor2.KeepFieldsUnique = true;
var list = new string[] {"1.pdf", "2.pdf"};
pdfEditor2.Concatenate(list, "3.pdf");
As a result, the file is opened with a proposal to sign it (the message box at the top of Acrobat "Click "Sign" to fill out and sign this form....")
How to remove this message and that form "3.pdf" can be edited and saved as forms "1.pdf" and "2.pdf" ?