Hi Hayley,
You can edit the text that appears on your quotes using the PDF themes option under your Settings menu. If you are considering sending quotes to your clients for approval, have you considered using the IRIS OpenSpace product? This is a free document sharing portal that allows you to request e-Approval for documents that are uploaded.
Unfortunately this doesn't directly integrate with KashFlow but will allow you to download and upload a document and then notify you once that approval has been received.