Adobe has redesigned the Acrobat interface multiple times since 2015. Many power users dislike the newer “simplified” ribbon and hidden toolbars. The 2015 Classic version offers the traditional toolbar layout that muscle memory still recognizes.
For everyone else: respect the software licensing, protect your systems, and adapt to the modern PDF landscape—your security is worth more than a nostalgic toolbar. Adobe Acrobat Pro Dc 2015 Classic Download
: Major vulnerability to exploits since updates stopped. Adobe has redesigned the Acrobat interface multiple times