Especially if you use headers in your document, you may like to apply different margins to some sections. Usually the initial sections (table of contents, etc.) and perhaps some final sections, or any sections that won’t use headers, should have different margins to avoid useless empty space at the top.

To apply different margins to multiple sections easily, you can just select those sections and open Word’s Layout > Margins menu. Word includes an option to change only “selected sections”. The option exists at the bottom of the relevant dialogue.

Note that to avoid making a mistake when you select the sections you’d like to change, you can switch to draft view where sections are clearly separated with a line that mentions even their id number.

If you are going to change all the initial sections, you can locate the last of them, place the cursor inside it, then press Shift+Ctrl+Home to select this and all the sections to the start of your document. Press Shift+Ctrl+End to to select all sections from the current to the end of your document.

Enjoy!