When I don't have page up and page down keys on my laptop..

[MIN HYUN5C2A]

So I need 

Page up

Page down keys for shortcuts

and My laptop doensn't have those keys

Does anyone know

any other alternative  key I could use other than page up and down keys, Please? 

[Rick Gerard]

On some laptops, the Function key changes the up and down arrow to Page Up and Page Down. On some laptops, the Fn key also simulates a Numpad with the keys something like 789uiojkl. There are also a few keyboard remapping apps for Mac and Windows.