
Description: Okular is a versatile document viewer software for KDE. It supports viewing PDFs, EPUBs, ODT, and other document formats. Okular allows annotating, highlighting, commenting on documents as well as filling forms.
Type: Open Source Test Automation Framework
Founded: 2011
Primary Use: Mobile app testing automation
Supported Platforms: iOS, Android, Windows

Description: Nitro PDF Reader is a free PDF viewer and editor that allows you to view, create, convert, edit, and sign PDF files. It has basic editing features like adding or removing pages, merging PDFs, adding text, comments or stamps, as well as more advanced features like OCR and batch conversion.
Type: Cloud-based Test Automation Platform
Founded: 2015
Primary Use: Web, mobile, and API testing
Supported Platforms: Web, iOS, Android, API