The only way to adjust sales invoice layout is via custom view templates. See Manager Cloud.
For a way to add a watermark, see [16.4.16] Added ability to use HTML markup in fields - #12 by Jon.
The only way to adjust sales invoice layout is via custom view templates. See Manager Cloud.
For a way to add a watermark, see [16.4.16] Added ability to use HTML markup in fields - #12 by Jon.