Hi Ben,
what do you mean by "workflow"? In our Sharepoint-Intranet we often use PDFs. We put them in document libraries and can open them there too.We don't use a workflow to publish the PDFs in the intranet.
But when we use the search engine and find the same PDF-Documents, we can't open them. We get the same error message that ist described in this thread.
But we can open them by right-click in the context-menu and open them in a new window or in a new tab. So the adress is correct ...
Hope this helps ...
Thomas