A method and apparatus are disclosed for forming a pattern of low basis weight regions, such as apertures or perforations, in an unbonded fibrous web. The present apparatus includes a forming surface having a pattern of forming elements, with an unbonded web positioned in operative association with the forming surface. Differential air pressure is applied to the web so that a pattern of low basis weight regions is formed corresponding to the pattern of forming elements. The fibrous web is thereafter removed from the forming surface, and can be further processed, if desired, such as by application of binders or other finishes, and can be integrated with associated components for various end uses, including medical, industrial, and hygiene applications.