Cross-references is a feature in Microsoft Word that allows you to do cross-references internally and automatically for footnotes that The Bluebook has you doing supras and infras for. This is one of the reasons why Google Docs is not very useful for preparing an article to be submitted to a law review and journal for publication.

To Add a Cross-Reference:

• Go to Insert --> Cross-reference.
  • This is either under the Insert tab or the Insert option at the top of your screen. Cross-reference is under the "Links" category if you are using the tab.
• Under "Reference type," click "Footnote."
• Under "Insert reference to," click "Footnote number."
• Make sure "Insert as a hyperlink" is checked.
• Under "For which footnote," select the footnote number you are wanting to supra or infra to. 
• Click "Insert."

To Update a Cross-Reference:

• Whenever you've made changes to footnotes (added new footnotes, deleted footnotes, etc.), to update the cross-references automatically, do the following:
  • Mac: command + a then f9 then when the prompt appears, click "Yes."
    • On my Macbook Pro, I need to hit fn, to then get the f9 button to work.
  • PC: ctrl + a then f9 then when the prompt appears, click "Yes."
• You can update the cross-references as many times as you need. 

[1] See Simon Canick, Library Services for the Self-Interested Law School: Enhancing the Visibility of Faculty Scholarship, 105 Lᴀᴡ Lɪʙʀ. J. 175, 178 n.17 (2013); Harriet Richman & Steve Windsor, Faculty Services: Librarian-Supervised Students as Research Assistants in the Law Library, 91 Lᴀᴡ Lɪʙʀ. J. 279 (1999).

[2] Rowena U. Compton, The Student Assistant, 23 Lᴀᴡ Lɪʙʀ. J. 24 (1930).

[3] Richman & Windsor, supra note 1, at 280.

[4] Compton, supra note 2.

When in a Microsoft Word document, the "1" and "2" in footnotes 3 and 4 will be hyperlinked to their respective footnotes 1 and 2. Additionally, if a new footnote was added at the beginning, the "1" and "2" would update to "2" and "3" once you followed the update instructions above.