I did almost the same with below code
TransientGeometry tg = invApp.TransientGeometry;
Matrix2d mx = tg.CreateMatrix2d();
//mx= skb[cbLetters.SelectedIndex].Transformation;
//---------------
double x = Convert.ToDouble(txtBoxXDir.Text)/10;
double y = Convert.ToDouble(txtBoxYDir.Text)/10;
double angle = Convert.ToDouble(txtBoxAngle.Text);
double oRad = (angle / 180) * 3.14159265358979;
mx.SetToRotation(oRad, tg.CreatePoint2d(0, 0));
skb[cbLetters.SelectedIndex].Transformation=mx;
mx.SetTranslation(tg.CreateVector2d(x, y));
skb[cbLetters.SelectedIndex].Transformation=mx;
invApp.ActiveDocument.Update();
but can i get some reference for Matrix and transformation