Final answer:
To add a shadow border in Word, open the Borders and Shading dialog box, choose the Page Border tab, select the Shadow option, customize if needed, and click OK to apply it to your document.
Step-by-step explanation:
To add a shadow border to your document using the Page Border tab in the Borders and Shading dialog box in Microsoft Word, start by opening the dialog box. Choose the Page Border tab, which will present different border options. From there, select the box that says Shadow, which will apply a shadow effect to your entire document's pages. Note that after selecting the shadow effect, you can also customize the color and width of the border if you desire. Once you have set your preferences, click OK to apply the shadow border to your document.