using(var doc = PdfDocument.CreateNew())
{
    var page = doc.Pages.InsertPageAt(0, 500, 500);

    //Create a file specification for the target document.
    var fileSpec = new PdfFileSpecification(doc);
    fileSpec.FileName = @"e:\0\1GB\test_big.pdf";

    //create destination in remote document
    var dest = new PdfDestination(doc);
    dest.IsSameDocument = false;
    dest.PageIndex = 99;

    //create a new bookmark (the bookmark will target the current document)
    var bookmark = doc.Bookmarks.InsertAt(0, "Title", page);

    //Create action dictionary
    var action = PdfTypeDictionary.Create();
    //Action type
    action["S"] = PdfTypeName.Create("GoToR");
    //file specification
    action["F"] = fileSpec.Dictionary;
    //destination in remote document
    action["D"] = PdfTypeArray.Create(dest.Handle);

    //set an action to a bookmark.
    bookmark.Dictionary["A"] = action;
    //remove the old destination from the bookmark.
    bookmark.Dictionary.Remove("Dest");

    doc.Save(@"e:\80\test.pdf", SaveFlags.NoIncremental);
}