You have to develop your module to add your fonts, since you are using Nati arabic font you can extended it by adding your fonts to document layout font selection field by inheriting the res.company as below:

from odoo import fields, models

class Company(models.Model):

    _inherit = 'res.company'

    font = fields.Selection(selection_add=[('almarai', 'almarai'),('Cairo','Cairo')])

Then you can select font from document layout but the font will be applied for Arabic and English. Also the fonts need to be installed in machine where Odoo is installed.