Long bond paper size in Microsoft Word is not included in the list of available sizes by default. However, you can manually enter the size using either centimeters or inches. A sheet of long bond paper has the dimensions 21.59 cm x 33.02 cm in centimeters and 8.5" x 13" in inches. Here are the steps to change the paper size to long bond paper in Microsoft Word:

1. Click on the "Layout" tab on the toolbar.
2. Click on the "Size" button and select "More Paper Sizes."
3. In the "Page Setup" window, go to the "Paper" tab.
4. Change the width and height to 8.5" x 13" or 21.59 cm x 33.02 cm.
5. Click "OK" to confirm the size of long bond paper in Word file.

You can also set long bond paper size as the default paper size in Word by following these additional steps:

1. Click on the "Layout" tab on the toolbar.
2. Click on the "Size" button and select "More Paper Sizes."
3. In the "Page Setup" window, go to the "Paper" tab.
4. Change the width and height to 8.5" x 13" or 21.59 cm x 33.02 cm.
5. Click on the "Set As Default" box before pressing "OK."
6. Click "Yes" to confirm setting.

After setting long bond paper size as the default paper size, you dont have to select the size again when opening Word.