The transitional Series
PA4 or L4
A transitional size called PA4 (210 mm × 280 mm or 8.27 in × 11.02 in), sometimes dubbed L4, was proposed for inclusion into the ISO 216 standard in 1975. It has the height of Canadian P4 paper (215 mm × 280 mm, about 8 1/2 in × 11 in) and the width of international A4 paper (210 mm × 297 mm or 8.27 in × 11.69 in), i.e. it uses the smaller value among the two for each side. The table below, shows how this format can be generalized into an entire format series.
The PA formats did not end up in ISO 216, because the committee decided that the set of standardized paper formats should be kept to the minimum necessary. However, PA4 remains of practical use today. In landscape orientation, it has the same 4:3 aspect ratio as the displays of traditional TV sets, some computer displays (e.g. iPad) and data projectors. PA4, with appropriate margins, is therefore a good choice as the format of presentation slides.
As a compromise between the two most popular paper sizes globally, PA4 is used today by many international magazines, because it can be printed easily on equipment designed for either A4 or US Letter. That means it is not as much a paper size than a page format.
A non-standard F4 paper size is common in Southeast Asia. It is a transitional size with the shorter side from ISO A4 (210 mm) and the longer side from British Foolscap (13 in, 330 mm) and is sometimes known as (metric) foolscap or folio as well.
A sheet of F4 can be cut from a sheet of SRA4 with very little wastage. The size is also smaller than its Swedish equivalent SIS F4 at 239 mm × 338 mm.