Emulate mouse wheel scroll with keyboard

It's possible with AutoHotkey.

Try this script for instance: Using Keyboard Numpad as a Mouse. It uses the Numeric Pad to emulate a mouse. When on, NumPad+ and Numpad- emulates the mouse wheel.

SerioSoft MKey does the job quite well.

This is much easier than making AutoHotKey scripts. TIP: If scroll doesn't work after making "scroll hotkey" try to change default scroll speed setting from "1" to "2".

You can also take a look at: AtnSoft Key Manager

This is not a generic answer to your question, but notice that some softwares such as Visual Studio Code allow the documents to be scrolled using a key combination as well, so you might want to check out the configuration of the software you're using the most for such shortcut key settings. In my case, it's Ctrl + Up/Down in VSCode by default to scroll down as much as one line, and Alt + PageDown/PageUp to scroll down the whole page a few more lines(more than one line) down and up. I've personally remapped the latter to Alt + z/x since it's easier for my hand.

(Assuming Windows): Check out AutoHotKey, it can remap the Mouse Wheel.

From the docs:

Mouse Wheel Hotkeys [Windows NT/2000/XP or later]

Hotkeys that fire upon turning the mouse wheel are supported via the key names WheelDown and WheelUp. WheelLeft and WheelRight are also supported in v1.0.48+, but have no effect on operating systems older than Windows Vista.