You can get and set PDF document metadata corresponding to a document's Info dictionary.  

You can also get and set the XMP metadata associated with a PDF or PostScript document.

To manage PDF metadata you can use the GetInfo and SetInfo methods of ImGearPDFDocument. The following example illustrates the usage of these methods:

public void SetMetadata(ImGearPDFDocument igPDFDocument)
{
    // If empty, set the dictionary key "Author" to "Accusoft."
    if (igPDFDocument.GetInfo("Author") == "")
        igPDFDocument.SetInfo("Author", "Accusoft");
    return;
}

Public Sub SetMetadata(igPDFDocument As ImGearPDFDocument)
    ' If empty, set the dictionary key "Author" to "Accusoft."
    If igPDFDocument.GetInfo("Author") = "" Then
        igPDFDocument.SetInfo("Author", "Accusoft")
    End If
    Return
End Sub