Open the WORD document and click Start, Border and Shading in the menu bar to enter the border and shading setting interface.

Click on the page border to enter this category. Under the page border category, click Box first, and then select the border line type you want in the style. In addition, you can also modify the border line color, border line width and so on.

After the above steps are completed, click "Apply to the whole document" in the lower right corner and click OK. After returning to the main interface, you can see that the addition of the outer border has been completed.