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.
Insert Symbol
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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.
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Insert Image
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."