you can put it in your template tag just before your header

Steps : 

1- add your font ttf in path : yourmodulename/static/src/fonts/DroidKufi-Bold.ttf          # For Example i used DroidKufi Font

2- You Have to create new path in static  : /static/src/css/style.css Make sure to add this code :

.font{
font-family:'traditional_arabic';;font-weight:100;font-size: 13px;   ### Here add your font family name
}

@font-face {
   font-family: 'DroidArabicKufiBold';
   src: url('/yourmodulename/static/src/fonts/DroidKufi-Bold.ttf') format('truetype');  
   font-weight: bold;
   font-style: normal;
     }

@font-face {
   font-family: 'DroidArabicKufiRegular';
   src: url('/yourmodulename/static/src/fonts/DroidKufi-Regular.ttf') format('truetype');
   font-weight: normal;
   font-style: normal;
}

.arabic{
   font-family:DroidArabicKufiRegular !important;
}

table.cr-table tbody tr:last-child
{
    height:100%;
}

3- add link rel path to your template then your style : 

Hi, Open this link i hope it's help you.

https://www.odoo.com/forum/help-1/question/how-to-add-custom-fonts-to-qweb-reports-88923

You can check this module this helps! 

https://apps.odoo.com/apps/modules/15.0/advanced_report_templates/

You can write style tag in custom report.

Ex:

<style>

@font-face {

font-family: myFirstFont; src: url(sansation_light.woff);

}

div {

    font-family: myFirstFont;

}

</style>

Using style tag you can use custom font in qweb report.

Thanks - but:  where do I have to put the font file on my local odoo server and how does the url have to look like?