PDFsharp & MigraDoc Foundation

pdfsharp v 1.0 Problem with free text (notes) in pdf
I open pdf with free text with document PdfDocumentOpenMode.Modify and put watemark and document is completly.
But when open pdf with watemark.
PdfDocumentOpenMode.Import and get the page whit this free text
outputDocument.AddPage(inputDocument.Pages(npag))
outputDocument.Save(outStream, False)
The free text disappears.
Somebody Know if pfsharp have probem with get this text notes when open for import and How can resolve it.

Thanks in avance.