Hi Jag,
Apologies for the late response to your question.
The customer will not be able to access any attachments added to the invoices, as part of their full statement. Invoice attachments are meant to be for internal purposes and are only accessible to the account users.
Unfortunately, it isn't possible to add attachments separately to statement emails either. But you do have the option to include an attachment when emailing invoices individually.
Also, I have removed the link you provided in your post due to it containing customer details. This is a public forum, so for security purposes, it is best that the link is removed. For future queries, you can email us at contact support where we can deal with any account information more securely.
If you have any further questions, please do let us know.
Kind Regards,
Natasha