i use odoo19, 

I create one custom module and i want to user are upload file and show the preview so what i do?

class PurchaseBuyer(models.Model):

    _name = 'purchase.buyer'

    _description = 'Purchase Buyers'

    sf_gst_certificate = fields.Binary(

        string='Upload GST Certificate',

        attachment=True,

        help='Upload GST Certificate as PDF'

      )

what is the view? 

how to possible pdf upload and preview in customization.