Final answer:
When customizing a sales invoice, you cannot preview the invoice before printing, but you can make changes to the labels, add logos/images, and avoid using a predefined Form Type.
Step-by-step explanation:
When customizing a sales invoice, there are certain limitations. You cannot preview the invoice before printing. You can, however, print a sample to review the changes made. Secondly, you have the capability to add logos or images to the invoice, which can help personalize the document.
Thirdly, you can change the labels for fields on the invoice, allowing you to customize the language and terminology used. Lastly, you have the freedom to avoid using a predefined Form Type and create a completely custom invoice layout.