Adobe Acrobat is the companion product to Adobe Acrobat Reader, an application that is able to open, read, create, modify and annotate files in the Portable Document Format (PDF). PDF files are used to publish and exchange electronic documents among knowledge workers world wide and Adobe Acrobat adds a additional collaboration features that support the edit-review-publish cycle.
Some applications like OpenOffice.org, Apple Pages and Apple Keynote provide a partly alternative to Adobe Acrobat, because they have built-in PDF creation capabilities.