Sales Quotes

Hi is there a way one can customise the lay out of the sales quotes, invoice and delivery notes?

This can be done with custom themes. But custom themes are considered obsolete features. (That is where they are found in Settings.) So they are no longer documented in the Guides. Replacement of the capability has been promised by the developer, but has not yet appeared.

What exactly are you trying to do? There may be ways to accomplish what you want.