You would have to purchase and provide an IcePDF Pro .jar on the classpath of every client; ICESoft separated the open-source core of their PDF viewer from their proprietary ‘font-engine’ and PDF write support. However, it looks like ICESoft is no longer selling new copies of IcePDF pro, so it’ s not really an option.
Within Vision, I don’t think there are a lot of options. The PDF support inside of the web browser module is just whatever Chromium has, and doesn’t have any support for annotation/markup, to my knowledge. You’d have to find some other Java Swing compatible PDF viewer/editor; or install a separate PDF editor on client machines and launch it in an editing mode, which is obviously a much worse user experience than directly editing within Ignition.