Paper sizes
The ISO 216 standard is the international standard for paper size. The standard includes the A4 size (297 x 210 mm), which is a common size worldwide for business and personal use. In the United States, Canada, and other North and Central America countries, Letter (8 1/2 x 11 inch) and Legal (8 1/2 x 14 inch) are common sizes.
While it's possible to print a document designed for one paper size on paper of a different size, a better experience is to support a page layout appropriate for the target market. When designing a page layout, you should ensure that the layout is responsive to changes in paper sizes. You should also ensure that the default page layout uses the appropriate page size for the target market.