Yes we have the option where invoices in Xero can be pulled back into the relevant contacts record inside our CRM. This would be in a PDF document.
We would also push contact updates from our CRM to Xero (one-way sync) – so that way you have the contact details available and we would know the Xero contact reference number so we would be able to associate the invoices back into the contact's record.
Please contact our Support Helpdesk to discuss further and for pricing.