Hi Alex,
Currently it is not possible to draw circle in table cells of grid model.
However, you can do this using flow model.
Here are some code to do this:
C#:
//Create a cell para
IParagraph para = table.Rows[0].Cells[1].AddParagraph();
//Create a ellipse in that cell para
EllipseShape ellipse= para.AppendCanvas(canvasSize).AddEllipse();
ellipse.Bounds = new RectangleF(380,55, 20, 20);
Here is a sample for your reference.
Circle_In_ITable.zip
Please take a look into it and let me know if you have any queries.
Regards,
Dhivya.