Wondershare PDFelement - All-in-one PDF editor
Autodesk DWG TrueView - Get a free DWG viewer to view, open, edit, and convert .dwg files, the native file format for AutoCAD files. DWG Trueview includes DWG TrueConvert.
Foxit PhantomPDF - Edit PDF files with our feature-rich PDF Editor. Download Foxit PDF Editor to convert, sign, scan / OCR & more. A speedy PDF Editor alternative to Adobe Acrobat.
Autodesk Design Review - Design Review lets you view, mark up, print, and track changes to 2D and 3D files.
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
ZWCAD Viewer - Cross-Platform .DWG | .DXF | .DWT R12-2013 Viewer