Where do I find the file uploaded to Google drive?

Question

Based on SO here, we are creating a pdf from a Google Document. The pdf is uploaded to Google Drive.

    self.GOOGLEDOCUMENTS_SCOPES = ['https://www.googleapis.com/auth/spreadsheets',
        'https://www.googleapis.com/auth/documents',
        'https://www.googleapis.com/auth/drive',
        'https://www.googleapis.com/auth/drive.file',
        'https://www.googleapis.com/auth/drive.metadata']
    
    # Set the permission for the google sheet
    self.documents_permission = {
        'role' : 'reader',            
        'type' : 'anyone',
        'value' : 'anyone'
    }


    document_credentials, document_project_id     = 
        auth.default(scopes=self.GOOGLEDOCUMENTS_SCOPES)  # Returns a tuple.                
        self.document_credentials    = document_credentials
        self.document_project_id     = document_project_id

1. We create the google document using the Google Doc API

            title = "file name for doc"
            body    = {                         
                'title': title,                        
            }
            document_service                = build('docs',     'v1', credentials=self.document_credentials)
            create_document_response        = document_service.documents().create(body=body).execute()
            document_Id                     = create_document_response.get("documentId")
   

2. We then use export_media to create a pdf of the google doc

                    media_pdf_request   = drive_service.files().export_media(fileId=document_Id, mimeType="application/pdf")                                                
                    file                = io.BytesIO()                                                
                    downloader          = MediaIoBaseDownload(file, media_pdf_request)
                    done                = False
                    while done is False:
                        status, done = downloader.next_chunk()                        
   
                    file_content        = file.getvalue()                        
                    file_metadata       =  {'name' : filename_statement,'mimeType': 'application/pdf'}                            
   
                    media                   = MediaIoBaseUpload(io.BytesIO(file_content),mimetype='application/pdf', resumable=True)
                    pdf_file = (
                        drive_service.files()
                        .create(body=file_metadata, media_body=media, fields="id")
                        .execute()
                    )
                pdf_file_name       = pdf_file.get("id")
   
                doc_res = drive_service.permissions().create(fileId=pdf_file_name,                    
                    body=self.documents_permission,                           
                    fields='id').execute()
   
                pdf_file_id     = doc_res.get('id')
   
                statement_link              = "https://docs.google.com/document/d/" + document_Id                            
                drive_link                  = "https://drive.google.com/drive/" + pdf_file_name            
   

We expect the file to be accessible at

drive_link                  = "https://drive.google.com/drive/" + pdf_file_name

Unfortunately we get a 404 error. Please help.

UPDATE -

We changed the drive link to the following -

drive_link = "https://www.googleapis.com/drive/v3/files/" + pdf_file_name

But we get at 403 error

{
  "error": {
    "code": 403,
    "message": "The request is missing a valid API key.",
    "errors": [
      {
        "message": "The request is missing a valid API key.",
        "domain": "global",
        "reason": "forbidden"
      }
    ],
    "status": "PERMISSION_DENIED"
  }
}