Final answer:
Keyboard shortcuts for stepping through frames depend on the software being used and are not related to PDF navigation. In PDF viewers like Adobe Acrobat, shortcuts like ← and Cmd-[ are used for page navigation, not frames. For frame navigation in video editing, consult the software's documentation.
Step-by-step explanation:
The keyboard shortcuts for stepping backwards or forwards by a specific number of frames, such as 8 or 10, varies depending on the software program you are using. However, the question seems to be mixing the concept of navigating PDF viewers or documents and stepping frames, which is more commonly associated with video editing or animation software. It's important to note that in PDF navigation, you don't step through frames but rather through pages or views. For example, in Adobe Acrobat on a Mac, you can navigate back and forward using the cursor or arrow keys - ← for back and X for forward. In Mac Preview, the shortcuts are Cmd-[ and Cmd-] to navigate back and forward, respectively. If you are working with video editing or animation software, you would need to check that specific program's documentation or settings to find the appropriate shortcuts for frame navigation.