In the xml file that defines your view, you can hide/show button using states attribute and/or attr attribute like:

<record id="your_form" model="ir.ui.view">

   <field name="name">your_form_name</field>

   <field name="model">your.model</field>

   <field name="arch" type="xml">

      <form string="Your Thing">

         <header>

            <button name="button_a" states="draft"/>   <!-- puts this button only when it's in draft state -->

            <button name="button_b" attrs="{'invisible': [('state', '=', 'draft')]}"/>  <!-- this button is always put in the form but it's invisible when shows this button if it's in draft state -->

        </header>