After the Header, we also need to add footer...
- from the Insert menu -> Footer, but only for Index and Default, because we don't want page numbers on the first page
- click into the footer of the index, then choose Insert -> Fields -> Page Number,
do the same in the footer for Default page.
As you may see your document has page numbers. Now, we'll do some magic...
- right-click to modify Index in the Stylist,
- change to the Page tab and
- choose roman letters.
Your index gets Roman page numbers, and our default text stays at Arabian numbers!
If you want to change the alignment of the page numbers in the Footer, all you have to do is...
- choose the paragraph styles in the stylist
- right-click the Footer -> modify
- click the alignment tab and choose the alignment you like.