Zoom in PDF Module with touch multipoint

Hi, I have a touch display “HMI ADVANTAGE” and display supports multitouch function (I know because I testing on web browser).
When I open a PDF file with PDF Viewer, I only can move the document (I can zoom with tools in PDF Viewer), but the zoom is not available with two finger at same time (multipoint).
In client side I sign in with “Touch Screen Mode”, and nothing change.
I also set the mode with “system.gui.setTouchscreenModeEnabled(True)” in a Script.
Anybody can help me? Please and thanks