When you need to produce documents on company letterhead but don't want to save on the expense and hassle of pre-printed paper, you might want to apply PDF watermarks and either send the document via email or print the document contents and letterhead at once. A watermark allows you to insert text and graphics across one or more pages in a document and place them in front of or behind page content.
Here's how to add a watermark in Acrobat:
Select Document > Add Watermark and Background.
In the dialog that appears, select 'Add a Watermark'.
Specify if you want the watermark to be displayed on screen or when printed.
Click 'Choose' to browse for the PDF source file that contains the watermark.
Specify the pages you wish the watermark to appear on.
Specify the fit, rotation and opacity of the watermark if you so wish and click OK.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.