The call number for papercraft is tt870, use this to cut down your search time. Go to the contents table 9. The paper formats defined by ISO in the A, B and C series are used today in nearly all countries apart from North America. You get the next higher format by cutting the paper in two equal pieces parallel to the shorter side. E.g. B1 is between A1 and A0.
Larger sizes have smaller numbers.
The ISO DL envelope format has the dimensions 220 x 110 millimeters. Have a look.