If you simply delete an attachment while you are in a page’s edit mode, it no longer will be shown within the page in view mode, but it is still attached to the page. To display all existing attachments, view the page then click on “Attachments,” or on the small paperclip near the breadcrumb link.
You’ll see the entire list of all the page’s attachments which you can then edit. Click on “Delete” and “OK” to completely remove an attachment.
If you delete an attachment that is still used within the page, you’ll see an error message “Unknown Attachment”. Resolve this error in edit mode by deleting the link to the attachment you have already deleted.
You can watch how to delete an attachment in our Video #21 of the Video Tutorial series “Learn Atlassian Confluence” and read more about attachments in general in Atlassian’s documentation.