Visit the official Adobe Acrobat Release Notes page. You can download the specific .msp update file for your version track here.
If you are experiencing crashes or errors with your existing 2015 installation, you can try these standard Adobe Repair Steps : Acrobat Pro DC very slow after update - Adobe Community
Acrobat Pro DC includes several security features that help you protect your PDF documents from unauthorized access.
Advanced optical character recognition for converting scanned docs to editable text. The Search for "Full Patch" and "Latest Fix"
However, it is important to note that Adobe Acrobat 2015 reached its end of support