The document provides instructions for resizing multiple photos at once using PhotoScape batch editor. The steps are:
1. Select the folder containing photos to resize and select all photos.
2. Drag the selected photos to the center area to add them for resizing.
3. On the right side, click the resize box and enter 640x480 to resize photos to a common online size. Click convert all.
4. Click save to resize the photos in the selected folder.