NVDA is a screen reader offered by NV Access, an Australian non-profit organization. NVDA is open-source and free for users to download and use.

All users encounter Flash-based content and PDF documents regularly, and Adobe wants NVDA users to have a positive experience. Therefore, Adobe is funding NVAccess to help address the goals to “Improve support for Adobe Reader” and “Add support for Adobe Flash embedded in Browsers. This work will benefit not only Flash and PDF, but also help users access content and applications developed with Adobe Flex and interactive forms developed with Adobe LiveCycle.
All tests were carried out with screen reader factory settings. JAWS in particular has a wide variety of settings controlling exactly what gets spoken. Screen readers allow users to interact in different modes, and can produce very different results in each mode. NVDA is the only screen reader we can trust to protect our privacy, to survive a decision by its founders to move onto other things in their lives and to be compatible with standards.
How To Use Nvda

Nvda Free Screen Reader
NVDA developers have already done some work to enhance access to PDF in the current release. We’re looking forward to additional improvements progress that will surely be made in the coming months!