PDF to Text - Free bulk conversion of PDF documents to plain text files, which can be opened by any text editor.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
Zamzar - Free conversion online of many type of documents (images, text, video, audio...
Document Viewer - Document Viewer is a highly customizable document viewer for Android. - SufficientlySecure/document-viewer
Online Convert - Convert files like images, video, documents, audio and more to other formats with this free and fast online converter.
Okular - Okular is a universal document viewer based developed by KDE.