I've posted one of the more coherent posts for everybodies perusal.
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It's not a patent for the keys themselves, but the practice of scrolling a specific amount regardless of the current view settings (eg. zoom). As such your keyboard is irrelevant, a peice of software that implements those keys in the standard way however is absolutely relevant.
To quote the patent text [uspto.gov] itself (emphasis added):
Briefly, the present invention provides a method and system for scrolling a substantially exact increment in a document, such as a row height corresponding to a row of one or more pages of a page set, so as to display a next page set from the precise vertical location into the page that the previous page set started, regardless of the current zoom percentage. For example, if the middle of a page set is at the top of the viewing area, after scrolling, the middle of the next page set is at the top of the viewing area. This operation occurs on receiving specific user input, e.g., a Page Up or Page Down key command.
Notice that the use of the Page Down/Up keys is an example of input that would be used in concert with the patent, so it's crystal clear that they're not trying to patent the keys themselves.
Not that what they're patenting is any less ridiculous, but let's at least get straight what ridiculous thing we're talking about.