Add a watermark to your Google Docs to indicate their state (draft, confidential, etc.) or to personalize them with your company's logo. Although Google Docs doesn't offer an official solution for those who wish to add a watermark to their documents, there is a method to overcome this limitation using only G Suite products.
Here's how to create a watermark for Google Docs and then add it to documents:
Start a new Drawing
Go toInsert and select Image
Add your logo or any other image you wish to use as a watermark
Resize and centre the image
Go to Format Options and select Adjustments
Increase the Transparency, just so your text would be visible over the image
Create a Text Box and place it over the image
Insert the text of your document. Make sure the font size is a few points larger than what you would normally use.
Start a new Document and Insert > Drawing from Drive
Insert the drawing you have just created as Linked to source
To edit the text, open Linked drawing options (top right of the drawing) and select Open source. Then edit the text inside the text box, return to the doc and click Update.
Although this workaround can be tedious for large documents, it’s currently the easiest way to add a watermark to Google Docs.