Resources that are coming up to the expiry on your account, will send an email notification. Your account may have had these added to your account under your Industry solution, you may not need all of these Resources.
When you receive a notification of expiry, you can find the document that it may be referring to, by going to Resources > View Resources > Expiring.
You will see a list of the documents that will be soon expiring. These would me documents that when initially uploaded, were also saved with an expiry date, in case they might require a new or updated document in the future.
In order to turn this notification off for Resource Documents, you can select the checkbox beside the document(s), and at the bottom of the page, options will appear - one of which is called Set Notification Groups. Selecting this will bring up a dropdown list, where you can select what groups should receive a notification, or select 'none' if you don't want any notifications to be sent for expiring documents. Then select Set Notification Groups in the green box to save the changes.
Alternatively, if you do need to update the Resource Document, then you can use this opportunity to Delete the old document and upload the new Resource.