public static void MyMethod(PdfPage page)
{
	var elements = FadeOut(page);
	//Render page here
	FadeIn(page, elements);
}




internal static List<PdfElement> FadeOut(PdfPage page)
{
	List<PdfElement> result = new List<PdfElement>();
	IEnumerable<PdfPageObject> formObjects = page.PageObjects.Where(x => x is PdfFormObject);
	foreach (PdfPageObject pdfPageObject in formObjects)
	{
		IntPtr handle = pdfPageObject.Handle;
		PdfFormObject obj = PdfFormObject.Create();
		result.Add(new PdfElement(handle, obj));
		obj.Copy(pdfPageObject);
		pdfPageObject.Transform(0, 0, 0, 0, 0, 0);
	}
	return result;
}

internal static void FadeIn(PdfPage page, List<PdfElement> fadeInElements)
{
	foreach (PdfElement pdfElement in fadeInElements)
	{
		var pageElement = page.PageObjects.FirstOrDefault(x => x.Handle == pdfElement.Handle);
		if (pageElement == null)
		{
			throw new InvalidOperationException("No element found.");
		}
		pageElement.Copy(pdfElement.PdfPageObject);
	}
}

internal class PdfElement
{
	public IntPtr Handle { get; private set; }

	public PdfPageObject PdfPageObject { get; private set; }

	public PdfElement(IntPtr handle, PdfPageObject pdfPageObject)
	{
		Handle = handle;
		PdfPageObject = pdfPageObject;
	}
}

public static void MyMethod(PdfPage page)
{
	var elements = FadeOut(page);
	//Render page here
	FadeIn(page, elements);
}




internal static List<PdfElement> FadeOut(PdfPage page)
{
	List<PdfElement> result = new List<PdfElement>();
	IEnumerable<PdfFormObject> formObjects = page.PageObjects.OfType<PdfFormObject>();
	foreach (PdfFormObject pdfFormObject in formObjects)
	{
		IntPtr handle = pdfFormObject.Handle;
		result.Add(new PdfElement(handle, pdfFormObject.Matrix.Clone()));
		pdfPageObject.Transform(0, 0, 0, 0, 0, 0);
	}
	return result;
}

internal static void FadeIn(PdfPage page, List<PdfElement> fadeInElements)
{
	foreach (PdfElement pdfElement in fadeInElements)
	{
		var pdfFormObject = page.PageObjects.FirstOrDefault(x => x.Handle == pdfElement.Handle) as PdfFormObject;
		if (pdfFormObject == null)
		{
			throw new InvalidOperationException("No element found.");
		}
		var matrix = pdfElement.Matrix.Clone();
        pdfFormObject.Matrix = matrix; //Does not work (pdfFormObject.Matrix = 0,0,0,0,0,0)
		pdfFormObject.Transform(matrix); //Does not work (pdfFormObject.Matrix = 0,0,0,0,0,0)
	}
}

internal class PdfElement
{
	public IntPtr Handle { get; private set; }

	public FS_MATRIX Matrix { get; private set; }

	public PdfElement(IntPtr handle, FS_MATRIX matrix)
	{
		Handle = handle;
		Matrix = matrix;
	}
}

internal static class Extensions
    {
        public static FS_MATRIX Clone(this FS_MATRIX matrix)
        {
            return new FS_MATRIX()
            {
                a = matrix.a,
                b = matrix.b,
                c = matrix.c,
                d = matrix.d,
                e = matrix.e,
                f = matrix.f,
            };
        }
    }

private Dictionary<IntPtr, FS_MATRIX> listOfMatrices = new Dictionary<IntPtr, FS_MATRIX>();

public void HideFormObjects(PdfDocument doc)
{
	foreach (var page in doc.Pages)
	{
		foreach (var obj in page.PageObjects)
		{
			var fo = obj as PdfFormObject;
			if (fo == null)
				continue;
			if (!listOfMatrices.ContainsKey(fo.Handle))
			{
				listOfMatrices.Add(fo.Handle, fo.Matrix);
				fo.Matrix = new FS_MATRIX() { a = 0, b = 0, c = 0, d = 0, e = 0, f = 0 };
			}
		}
	}
}

public void ShowFormObjects(PdfDocument doc)
{
	foreach (var page in doc.Pages)
	{
		foreach (var obj in page.PageObjects)
		{
			var fo = obj as PdfFormObject;
			if (fo == null)
				continue;
			fo.Matrix = listOfMatrices[fo.Handle];
		}
	}
}