Headers - adding Page number with 4 digit padding (leading zeroes)

[m2ramos]

For the life of me, I can't seem to figure out how to add page numbers that are 4 digits long.  So the pages look like the following:

0001, 0002, 0003, etc

I tried to Google it but it's not showing any results for what I need.  Can anyone assist?

[Bernd Alheit]

How does you add the page numbers?