Developed by the ICT-Accessibility Lab of the Zurich University of Applied Sciences (ZHAW) in collaboration with the Swiss Federation of the Blind and Visually Impaired, PAVE (PDF Accessibility Validation Engine) is an award-winning web service designed to evaluate and improve the accessibility of PDF documents.
When you upload a PDF document to the service, Pave will show a list of the accessibility issues found in that document; after that, it will apply fixes for those issues that can be fixed automatically (i.e. with no manual intervention by the user). Then, it will guide you through a process to perform manual testing for various accessibility issues that can be fixed only manually, providing all the tools that are necessary to fix them (aca manual tagging!).
While the service runs in the cloud, it provides the ability to delete each document from the server immediately after you finish working on it.