1. Tap the Thumbnails icon on the bottom navigation bar.
2. Select the range of pages you want to modify, then tap on the Overflow button and select Modify page labels:
4. In the Modify page labels dialog, you can customize the appearance of your page label. If you would like, you can also change the range of pages to modify.
Below is a short overview of this dialog:
a. Select the pages you would like to modify.
b. Preview of the page label.
c. Customizable page label numbering properties.
You can preview the page label before committing the changes.
5. Tap OK to finalize the changes: