This section gives the ability to add documents while issuing the invoice. Here, the attachment would only be visible to your team and not the receiver of the invoice, like the Memo note at the bottom part. 

Follow the steps below to add private documents that are available ONLY to admins in the invoice:

• Go to Accounting > Invoice
• Create the invoice (this feature works for Tenant and Owner invoice creation only)
• On the last part of the invoice, you will notice that there are document sections that you can use
• 1. Documents (Viewable to everyone)
• 2. Private Documents (Only admin can view and download)
• In this case, choose and upload the document in Private Documents
• Once done, click ‘Submit’