Click the Create New Rectangle tool
or the Create New Ellipse
tool.
Position the pointer on a page of the PDF document
and do one of the following:
To draw a new rectangle or ellipse, drag
diagonally.
To draw a square or circle, hold down the SHIFT key while
dragging.
To draw a rectangle or ellipse, starting from its
center and not from its side, hold down the ALT key (Windows) or
Option key
(Macintosh) while dragging.
Drawing from side keeps the sides of the shape
in a fixed position along the x and y axis
Drawing from center keeps the center point in
a fixed position.
To draw a square or circle, starting from its
center, hold down both the SHIFT key and the ALT key (Windows) or
Option key
(Macintosh) while dragging.