Most PDF documents have more than one page. And some GIF images have frames for animation, which are called Animated GIF. Besides, ToyViewer can display TIFF Stacks, which have more than one frame in a file.
You can show a control panel by clicking "Multi-Page..." of the menu "Tools". You can also use the context menu or the short cut "Command-shift-i". When an image with plural pages (or frames) is displayed on the active window, the total number of pages and the current page index are shown on the panel. You can show the next or the previous page using the buttons, and you can also jump directly to a page specifying its page index.
You can also specify the page using the wheel on the panel. If the button is checked, as the wheel are moved, the series of frames are displayed smoothly.
You can apply rasterizing to a PDF document, and you can also apply clipping or other operation to an animated GIF. But, the operation affects only the currently displayed single page or frame. For example, clipping operation to an animated GIF does not make a smaller animated GIF. It makes a smaller single image.