Is it possible to somehow find out the value of radius of rounded rectangle corners in Illustrator CS4? I know one could just click with Rounded Rectangle tool after drawing the rectangle to display the last used value of the radius but what if it is an old document with many different rounded rectangles?
It is basically the same question as this one, but this time the question is about AI CS4 - not Photoshop.
You can use the exact same technique as the linked question. You just measure the difference in point positions.
If you are working in pixels, turn on pixel preview (View -> Pixel Preview) and count the number of pixels rows from one point to the next.
If you are working in any other units, just calculate the difference in the points X/Y position. You can see a points position in the Transform panel.
You can see in the example the Y position of the points are 140pt and 150pt. The difference between those points is 10pt = the corner radius you are looking for is 10pt.