Here is my Certified CAcert Assurer certificate, which has been digitally signed by CAcert education officer Bernhard Froehlich. Verifying his digital signature on that PDF is a little more difficult than one might hope, as neither Preview on OS X or the GNOME equivalent have any such facility. The only PDF viewer I know of which can perform the task is Adobe Reader.
To verify the signature on that document with Adobe Reader you need to import the CAcert class 1 root certificate into Adobe Reader and mark it as trusted.
To do this in Reader 9, open the Document Menu and select Manage Trusted Identities… then click the Add Contacts… button in the dialog box which appears. That brings up another dialog box, in which you click Browse… to get a standard file selection window in which you should select the file containing the CAcert Class 1 root. Selecting the file takes you back to the dialog titled Choose Contacts to Import. Now select the certificate you just added in the top box of that dialog and click Trust…. Ensure that both Use this certificate as a trusted root and Certified documents are ticked. Click OK, then Import, and finally Close. And you’re done.
I’ve tested the above process on my Linux and OS X laptops; hopefully the same mechanism works on Windows.
