Under File menu you have:
-Page setup...
-Print preview...
-Print...
-Print to PDF...

The Page setup popup have:
- on top: Page format button ---> size, orientation, borders
- on bottom:
-- 2 fields: Header: and Footer:
-- Variables:
When you click on Header or Footer field the Variables became active.
The 3-th from left is the scale. You could also add some text in the front of it like "Scale: $planScale"