VBA to adjust size of existing footers

Your question can be answered with any value on a scale from "Easy" to "Impossible". Here is the problem.

1. Excel stores the footer texts as just plain text, for example "Left". The text will be displayed and printed in the default font.
2. When the text is supposed to be displayed in another font the instruction is added to the text itself., like "&"Aharoni,Bold"&12Left". The font definition is preceding the text. One might be tempted to split the string on the font size to retrieve the original text, but if the footer text starts with a number Excel isn't consistent, it inserts an extra space: "&"Aharoni,Bold"&12 11Left"
3. And then there is the chance that different parts of the footer might be formatted with different fonts, like &"Aharoni,Bold"&12Left &"Aharoni,Underlined"&14 11Right left"

Therefore the verdict is that all depends upon whether you know what's in the footers. To get at the problem is to extract the text from the footers and either delete all font formatting or add the desired font formatting. If your footers have standard items, like worksheet name, date, page number etc. (incl. cell references) that wouldn't be too hard to do. But ...