I see that you can add an attachment to a sales invoice, and either make it visible to the customer, or keep the customer from seeing it. Training videos only indicate that you can attach a file to a sales invoice using the attachment icon. I can see that there is a button available after I attach the invoice, but I can't find any information in the knowledgebase or training videos on if the attachment is visible to the customer with the button 'on or 'off'.

