1.Press Ctrl+H to display the Replace tab of the Find and Replace dialog box.
2.Click the More button, if it is available.
3.Click the Use Wildcards radio button.
4.With the insertion point in the Find What box, click Format and choose Style. Word displays the Find Style dialog box.
5.Locate and click on the Footnote Reference style.
6.Click OK to close the Find Style dialog box.
7.In the Replace With box enter the following: ^&
8.Click Replace All.
The purpose of these steps is to try to remove any confusion that Word may be experiencing and cause it to renumber all the footnotes. If this approach doesn't work, try just a bit of a different approach:

1.Press Ctrl+H to display the Replace tab of the Find and Replace dialog box.
2.Click the More button, if it is available.
3.Make sure the Use Wildcards radio button is cleared.
4.With the insertion point in the Find What box, click No Formatting and enter the following: ^f
5.In the Replace With box enter the following: ^&
6.Click Replace All