Adding Custom button like print in all doctype views

How we can add custom icon button in all doctype views . I mean how we can extend doctype view to have our custom button same as print button in form view

Hello please check this.

Hi, thanks for your quick response.
Actually i want to extend form view and want to add my button in formview of in all the doctypes.
i want to create a utility button in all doctypes where i can export the doc to word document like that.
above thread provides info to add custom button in a specific doctype only

Use form.js and add custom button there using this