Here is example of how you use custom font in your QWEB Reports.

<template id="report_product_image"> 
   <t t-call="report.html_container">
      <t t-foreach="docs" t-as="o">
        <div class="page"> 
         <style type="text/css">
          <![CDATA[/* United */
          @font-face { font-family: ';Comic Sans';
          font-style: heavy;
          font-weight: 300;
          src: local('United'), url(/home/emipro/Desktop/Tejas/comic-sans.otf) format('opentype');
        } 
        ]]>          
        </style>

style="font-family: yourfont;"