: A free, browser-based tool that lets you view and share 2D and 3D designs without installing any software. Autodesk Design Review

: A free, lightweight application for marking up, printing, and tracking changes to 2D and 3D files. Fusion 360

: Included with the standard Inventor installation, this allows you to open and view all Inventor file types (ipt, iam, idw, etc.) without a paid license. Autodesk Viewer (Online)

Portable inventor to save harddrive space - Autodesk Community