AutoCAD: 旧バージョンで新バージョンファイルを開く https://knowledge.autodesk.com/ja/support/autocad/troubleshooting/caas/sfdcarticles/sfdcarticles/JPN/Error-The-drawing-file-cannot-be-opened-because-it-was-created-with-a-more-recent-version-of-AutoCAD.html https://www.autodesk.com/products/dwg/viewers
