You can add a substitute box instead of image thumbnails. This improves performance because image thumbnails do not need to be created.

In config.js, set the doNotLoadPageThumbs parameter to true to display substitute boxes instead of image thumbnails. The default value is false.

If the doNotLoadPageThumbs parameter is set to true, VirtualViewer will not request thumbnail images. Instead, VirtualViewer displays a box with the page number. Select the substitute thumbnail box as you would an image thumbnail.

doNotLoadPageThumbs: true,

Use the thumbPageLabel string to set the page thumbnail tooltip. Please note that it is important to include the trailing space in "Page ":

"thumbPageLabel": "Page "