Tick the "Access Task Document" group.

Now go to the task and attach the document.

You can see the document without download using the document smart button.

After press on the document smart button, it opens the document kanban view.

In the document form view tick, the "Expiry Date Notify?" to get expiry date email notification.

You can see the document without download that document.

You can send email notifications to multiple customers using the "Notify Email" option.

You can send the notification manually by modifying scheduled actions.

Manually sends email notifications without scheduled actions.

The email notification form view looks like this, you can see the document from here.

You can send multiple customers emails manually also.

Tick the "Notify Customer" to send document expiry notification to the customer only.

Email notification list view.

Email notification form view, you can also see the document from here.

You have to tick "Expiry Date Notify?" to get an email notification on the expiry date.

Tick/untick "On Expiry Date Notification" to enable/disable email notification on the expiry date.

It sends email notifications based on the configuration.

The email notification form view looks like this.

The task kanban view looks like this.