ezPDF Reader!

Foxit Reader is a free and light-weight multi-platform PDF document viewer. Its core function is compatible with PDF Standard 1.7.

Evince is a document viewer for multiple document formats. It currently supports pdf, postscript, djvu, tiff, dvi, cbr, cbz, etc.

PDF-XChange Viewer is an alternative viewer for PDF files that enables you to view and annotate PDF files. You can add text, sticky notes, and other annotations and save them to the file, which will be compatible with the standard Adobe Acrobat Reader DC .The PDF XChange Viewer is an excellent tool for converting not text-searchable pdf-files in text-searchable pdf-files.

Okular is a universal document viewer based on KPDF for KDE 4 with support for advanced document features, such as annotations, forms, and embedded files.

The smallest, fastest, most feature-rich PDF editor/viewer available

qpdfview is a Qt-based tabbed document viewer using the Poppler library for PDF rendering and CUPS for printing. Support for the DjVu and PostScript formats can be added via plugins.

Xodo is the ultimate cross-platform PDF viewer and annotator. And it’s 100% free.

With GoodReader on your iPhone, iPod Touch or iPad, you can read virtually anything, anywhere. Books, movies, maps, pictures; GoodReader puts it all in a single app, right in your pocket.

Besides exceptionally fast launching and displaying speed, Gaaiho Reader is reliable in printing, filling forms annotating documents and adding bookmarks.

qAllInOne (aka qAIO) is a free open-source software built using Qt to provide users an All-In-One media player, so it can view images, play videos and audio.

PDF Expert lets you read and annotate PDF documents, highlight text, make notes and save these changes being compatible with Preview and Adobe Acrobat. Moreover, PDF Expert is the only iPhone application that can fill PDF forms!

Atril is a simple multi-page document viewer. It can display and print PostScript (PS), Encapsulated PostScript (EPS), DJVU, DVI, XPS and Portable Document Format (PDF) files. When supported by the document, it also allows searching for text, copying text to the clipboard, hypertext navigation, and table-of-contents bookmarks. Atril is a fork of Evince.

The application allows you to directly open and read PDF files that have been saved to your media card – without the need for server-side conversion, services or subscriptions.