Autodesk no longer distributes older versions like 2015 for free to the general public. However, there are two primary ways to access it legally: Education Plan
and lack official security signatures. If you are a student, you can access current versions of AutoCAD for free through the official Autodesk Education plan Safeweb (Norton) Intro to AutoCAD 2015 - 16 - Paper Space Autocad 2015 Filecr
While AutoCAD 2015 is a legacy version of the industry-standard Computer-Aided Design (CAD) software, the pursuit of unauthorized versions carries significant risks and legal implications. Autodesk no longer distributes older versions like 2015