The software giant applied for the patent in 2005, and was granted it on August 19, 2008. US patent number 7,415,666 describes "a method and system in a document viewer for scrolling a substantially exact increment in a document, such as one page, regardless of whether the zoom is such that some, all or one page is currently being viewed".
The patent's listed 'inventors' are Timothy Sellers, Heather Grantham and Joshua Dersch. However, Page Up and Page Down keyboard buttons have been in existence for at least quarter of a century, as evidenced by this image of a 1981 IBM PC keyboard.
"In one implementation, pressing a Page Down or Page Up keyboard key/button allows a user to begin at any starting vertical location within a page, and navigate to that same location on the next or previous page," reads the patent's summary.
"For example, if a user is viewing a page starting in a viewing area from the middle of that page and ending at the bottom, a Page Down command will cause the next page to be shown in the viewing area starting at the middle of the next page and ending at the bottom of the next page. Similar behavior occurs when there is more than one column of pages being displayed in a row," states the summary.
Microsoft has a long history of applying for, and being granted patents for, inventions that many argue--and can sometimes demonstrate--were based on earlier work carried out by others, or based on a common, self-evident idea.
One example is the company's patent on a mouse wheel that can scroll up and down; another is its patent on double-clicking buttons. The company received its 5,000th patent from the US Patent and Trademark Office in March 2006, and is currently approaching the 10,000 mark.