You probably need to look into documentation to the library you are using. They might have a forum of their own, or a mailing list or some other way to contact the developers. The error text isn't any of the built-in Flash errors - that's something the developers of the library decided to add, and as it usually happens with error messages, they are cryptic and uninformative
To help others to at least recognize your problem, you could at least tell what library are you using - generating PDF files isn't anything very common to do in AS and very few people may know what library you are talking about.