How do I have my application already implemented in Heroku present the filefield of Django?

Question

In my localhost my app works fine, but when I do deploy in the heroku it does not show uploads of my. pdf files

MODEL.PY
from django.db import models
from django.contrib.auth.models import User

# Create your models here.


class Client(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    protocol = models.CharField(max_length=15, null=True)
    name = models.CharField(max_length=50, null=True)
    number = models.CharField(max_length=18, null=True)
    phone = models.CharField(max_length=10, null=True)
    active = models.BooleanField(default=True)
    pdf = models.FileField(upload_to='pdfs')

    def __str__(self):
        return str(self.id)
VIEW.PY

from django.shortcuts import render, redirect
from django.contrib.auth.decorators import login_required
from .models import Client

URLS.PY

from django.contrib import admin
from django.urls import path
from base import views
from django.contrib.auth import views as auth_views
from django.contrib.staticfiles.urls import static
from django.contrib.staticfiles.urls import staticfiles_urlpatterns
from . import settings


urlpatterns = [
    path('logout/', auth_views.LogoutView.as_view(), name='logout'),
    path('', auth_views.LoginView.as_view()),
    path('main/', views.main),
    path('admin/', admin.site.urls),
]

urlpatterns += staticfiles_urlpatterns()
urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)


@login_required
def main(request):
    client = Client.objects.filter(active=True, user=request.user)
    return render(request, 'main.html', {'client': client})

def logout(request):
    return redirect(request, 'registration/login.html')

TEMPLATE
{% extends "body.html"%}
{% block content %}

<div class="card-columns">

{% for c in client %}
    <div class="card border-primary mt-3 ; ml-2" style="width: 30rem; height: 700px">
        <div class="card-header text-white bg-primary border-primary" style="font-size: 30px; text-align: center">DADOS</div>
            <div class="card-body ">
                <h2 class="card-title text-primary">CNPJ/CPF:</h2>
                    <p class="card-text" style="font-size:30px">{{ c.number }}</p>
                <h2 class="card-title text-primary">RAZÃO/NOME:</h2>
                    <p class="card-text " style="font-size:30px">{{ c.name }}</p>
                 <h2 class="card-title text-primary">PROTOCOLO :</h2>
                    <p class="card-text" style="font-size:30px">{{ c.protocol }}</p>
                 <h2 class="card-title text-primary text-primary">CONTATO:</h2>
                    <p class="card-text" style="font-size:30px">{{ c.phone }}</p>
            </div>
         </div>

         <div class="card-columns ">
            <div class="card border-primary mt-3" style="width: auto; height: 700px">
                <div class="center ">
                    <iframe height="690" src="{{ c.pdf.url }}" width="800"></iframe>
                </div>
            </div>
         </div>
    {% endfor %}
</div>