A4 is a very common paper size. Most office documents seem to favour this paper size. Student notebooks take on this size and shape. A4 Problem? There is no problem with A4. The problem is created when digital documents that are designed for reading online are assigned physical sizes and aspect ratios that were designed for printed documents. The most problematic such format is PDF. Why is PDF a Problem? PDF is not the problem. The problem is created by the absence of an option to change the document's aspect ratio at the time of saving it. Most computer monitors use the 16:1 (widescreen) aspect ration. Ideally, PDF readers should allow the user t o set the aspect ratio to use when reading the document. PDF creators should offer a number of common ratios as a minimum or , even better, set no fixed aspect rati o but leave this to the reader. Fixed is Bad PDF is not a responsive e-document format unlike ePub. Its a fixed layout format. Fixation is a key strength