HP OfficeJet Pro7740 wrong scale of pages / thick borders

At least the driver is eliminated as a cause of the issue. What does the following command report?
locale

These may be worth reviewing re paper size:
Changing default paper size is not retained - #4 by Tomek?
How do I change default paper settings from "letter" to "A4"? - #19 by erAck - English - Ask LibreOffice

Let’s see what others can recommend as well.