Check out the dimensions and templates on Designs.ai for one of the most widely used paper sizes.
The paper size of A4, 21 x 29.7 cm (21 x 29.7 cm) is the most popular size in ISO 216, and is used worldwide in most countries, except in the United States, Canada and some parts of Mexico. In the North American paper size series, its closest equivalents are Letter and Legal. A4 is a little longer than the letter and a little shorter than the legal letter and slightly narrower than both.
A4 is widely used in various personal and professional settings. A4 paper can be used to produce a wide range of communication and promotional materials, such as correspondence with flyers, summaries, magazine official forms and catalogs.
DL paper series
The DL (Dimension Lengthwise) envelope usually goes together with A4, being exactly one third of its size. Thus, DL is a common size for envelopes that can hold a sheet of A4 folded into thirds, With Compliments slips and is also used for promotional materials such as brochures, flyers, cards, and invitations.