I don't know which version you are using. Write down two versions, you can choose.
WORD2003
1. Position the cursor at the end of 1 page, and click "Insert-Delimiter-(section break Type) Next Page" in the menu bar. Press ok. Ibid., insert another section break at the end of page 3.
2. Click View-Header and Footer, position the cursor at the footer of page 2 (that is, section 2), and click the "Link to Previous Page" button in the header and footer toolbar to make it exit the highlighted state. As above, in the footer of page 4 (that is, section 3), click the "Link to Previous Page" button to make it exit the highlighted state. At this point, you can see that the words "same as a section" on the right side of the footer have disappeared.
3. Position the cursor anywhere on page 2, click Insert-Page Number, click Format, set the page number format to I, ii and iii, select Start Page Number, enter I, and press OK twice.
4. Position the cursor anywhere on page 4, click Insert-Page Number, and then click Format. The number format is set to 1? 2? 3. Select "Start Page Number", enter 1 and press OK twice.
WORD2007
1. Position the cursor at the end of 1 page and click "Page Layout-(Page Setup) Delimiter-(section break) Next Page". Ibid., at the end of page 3, insert another section break.
2. Double-click the footer on the second page to enter the editing status of the header and footer, and click the "Link to the previous page header" button in the toolbar to exit the highlighted status. In the footer of page 4, click the "Link to Previous Header" button in the toolbar to make it out of the highlighted state.
3. Position the cursor on page 2, click "Insert-Page Number-Format Page Number", set the numbering format to I, ii and iii, select "Start Page Number" as "I", and then click "Insert-Page Number-Page Bottom-Ordinary Page Number 2". ?
4. Position the cursor on page 4, click "Insert-Page Number-Format Page Number" and set the numbering format to 1? 2? 3? , select Start Page Number as 1, and then click Insert-Page Number-Page Bottom-Common Number 2.