In the preview area, thumbnails (miniature images) may appear for each page of a document that is selected in the document tree. If the document has multiple pages, click any of the thumbnails to preview the corresponding page. Only documents of the following file types have thumbnails: .bmp, .gif, .jpg, .png, .tif, and .pdf.
Notes:
For .pdf files, the thumbnails are displayed using the controls of the program that handles .pdf files.
If the thumbnails for a bmp, .gif, .jpg, .png, or .tif file are not visible, on the View menu, the Show Thumbnails in Preview option does not have a check mark next to it. To show thumbnails, click Show Thumbnails in Preview.
If the thumbnails for a bmp, .gif, .jpg, .png, or .tif file are visible, on the View menu, the Show Thumbnails in Preview option has a check mark next to it. To hide thumbnails, click Show Thumbnails in Preview.