I figured this out alone.
Here's the solution to set the font size to 10 (change that number to get the font size you want):
Code:
.CenterFooter = _
"&""Arial Black,Normale""&10&K339966MY COMPANY Ltd" & Chr(10) & "VAT registration No. GB 111 1111 11" & Chr(10) & "Registered in England and Wales No. 1111111"