The software needs to be registered using your proxy account that is used for the SQL Agent. You know how when you install some new software on the box, it works just fine for you, but when another user logs in, they get prompted with a model dialogue box when they go to use the software for the first time.

Although I'm not 100% positive on the syntax, from the command prompt try:

C:\runas /user:YOURDOMAIN\useraccount "C:\ProgramFiles\PrintHtml.exe"

This executes the application as that user and once the prompts and license information is entered (once) everything works as it should without any prompting.

Not sure this applies to your scenario but thought I'd share the experience - best of luck!