OfficeSuite 8 is an application available on iOS and Android platforms. This allows to open many formats including Microsoft formats (doc, docx, docm, xls, ppt, pptx …), OpenOffice (odt, ods and odp), in addition to rtf, txt, log, csv, eml, zip. No constraint in terms of compatibility, therefore.
For PDF, some tools allow you to add comments and annotations. The edition, available only in a paid version, is still strongly represented within the app; a way to force the purchase that will not be to everyone’s taste.
An option allows you to connect the application to its cloud service (s) such as Box, Dropbox, Google Drive, OneDrive, Amazon Cloud Drive or SugarSync.
Note that the paid version of the software adds a spell checker, in addition to many tools and possibilities. In particular to convert its files from a PDF to a desired format.