Adobe has officially discontinued the sale of Acrobat 2015. This means you cannot simply go to the Adobe store, buy a license, and download it fresh. However, the installer files are still accessible for those who previously purchased the software.
: For those who purchased physical copies, the original DVD-ROM is the most reliable way to reinstall the software. Key Features of the 2015 Classic Release Adobe Acrobat Pro Dc 2015 Classic Download