Any number of files can be attached to invoices, quotes, credit notes or purchase orders.
Optionally, you can choose to attach the file to the email used to send the invoice to a customer or PO to a supplier.
You manage the attachments for a document while editing the document. For example, to manage the attachments for an invoice, open the invoice by double-clicking the invoice in the Invoices & Payments tab or selecting the invoice and pressing the Open button.
In the Full Invoice View form, select the Attachments tab as shown in the following picture: