PdfMergeKeepFieldsSeparate Property

A flag indicating if the form fields with the same name coming from different documents are kept as separate fields. When true, the fields of a document whose names were already used by a previous document are renamed with a numeric suffix and keep their own values. When false, they become a single field with the value of the first document and the widgets in all the documents. The default value is true

public bool KeepFieldsSeparate { get; set; }