Update Attachments
FTP Attachments® Pro comes with a custom link called “Update Attachment” which is used to attach the same file with updated information. By doing this, you will be able to maintain versions of your attachments so that you can go back in history and get the older version of the document or file.
Make sure you have created the custom link button for updating the attachment and added it to the Layout.
Search for the particular object to which you attached the file.
Click on the attachment in the FTP Attachments® related list section.
Click on the “Update Attachment” link button in the FTP Attachments® screen, this will take you to the update page.
Use the “Upload” button to select the file, which you have updated, to upload. Enter the comment for the attachment (Optional) Click on “Attach”.
Click on the “Done” button it will redirect you to the record page of the Salesforce instance