You can use Microsoft Word's Insert tab or a keyboard shortcut to place a reversible reaction arrow into a document, or you can insert an image of the symbol from your computer or a Web page. Do not use an image from the Internet unless it is free to use or you have the copyright owner's permission.
In the Insert tab, click on the "Symbol" drop-down menu and select "More Symbols." Click on the Subset drop-down menu and select "Arrows." If you don't see this option, select "Times New Roman" in the Font drop-down menu. Click on the reversible reaction arrow and then click the "Insert" button. Alternatively, you can type "21cb" into your document (without the quotes) and then press Alt+X and Word will insert the arrow.
Click on the "Pictures" button in the Insert tab and from there you can navigate to and select the picture on you computer. Another approach is to right-click an image in a Web page and select "Copy" and then right-click in your Word document and select "Paste."