Adobe Acrobat Reader is described as 'View, annotate, and collaborate on PDFs, utilize cloud storage and freehand tools. Upgrade for editing and converting to other formats' and is a very popular PDF Reader in the office & productivity category. There are more than 100 alternatives to Adobe Acrobat Reader for a variety of platforms, including Windows, Web-based, Linux, Mac and Android apps. The best Adobe Acrobat Reader alternative is SumatraPDF, which is both free and Open Source. Other great apps like Adobe Acrobat Reader are Okular, Foxit PDF Reader, Evince and Firefox PDF Viewer (PDF.js).
The pdfDocs UI is intuitive, the whole application has the same feel as Microsoft Office.