InvoiceOcean allows you to edit and permanently save custom document names. The following documents are subject to edit:  

• Invoice
• Receipt
• Proforma Invoice
• Bill
• Correction note
• Estimate
• Not accounting document
• Final Invoice
• Service import from EU
• "Vat margin"
• Accounting note
• Credit Note
• Other invoices
• Pre-invoice
• Service import

In order to name your own documents, go to Settings > Account settings > Print settings > Custom document names