PDF Accessibility Checker 3 (PAC 3)^[8] by Access For All is a freeware utility for Windows that checks PDF files for PDF/UA conformance. The program implements the Matterhorn Protocol checks. When you open a PDF file in PAC 3, the program runs its checks and shows a summary of the results. Since there is no interactive checking, the program can only warn about some of the failure conditions that require human checking. Unfortunately, the program also has some bugs in its checking.

Figure 11. PAC 3 PDF/UA checker