Here I want to set the already exist PDF document properties under Initial View tab in acrobat.
Document Options:
The two items Show = Bookmarks Panel and Page and Page Layout = Continuous are controlled one layer up from the ViewerPreferences in the document's /Catalog. You can get to this via:
stamper.Writer.ExtraCatalog
In your case you're looking for:
// Acrobat's Single Page
stamper.Writer.ExtraCatalog.Put(PdfName.PAGELAYOUT, PdfName.ONECOLUMN);
// Show bookmarks
stamper.Writer.ExtraCatalog.Put(PdfName.PAGEMODE, PdfName.USEOUTLINES);
The items Magnification = Fit Width and Open to Page number = 1 are also part of the /Catalog but in a special key called /OpenAction. You can set this using:
stamper.Writer.SetOpenAction();
In your case you're looking for:
//Create a destination that fit's width (fit horizontal)
var D = new PdfDestination(PdfDestination.FITH);
//Create an open action that points to a specific page using this destination
var OA = PdfAction.GotoLocalPage(1, D, stamper.Writer);
//Set the open action on the writer
stamper.Writer.SetOpenAction(OA);