In IntelliJ, can I make PageUp, PageDown move by smaller increments?

I had taken @yole's answer and implemented all of the actions he had described in a separate plugin:

There is no way to control this through the settings. What you can do is write a plugin that performs scrolling in the way that you prefer. It's fairly easy: all you need to do is copy the existing PageUpAction/PageDownAction classes and the methods they call (EditorActionUtil.moveCaretPageUp/Down) to scroll by as much as you want.

This plugin implements new actions "Partial Page Up" and "Partial Page Down" which allow one to scroll a configurable size of screen definable in the usual IDEA settings dialog.

There's an installable version of the plugin in official JetBrains repository.