"It looks like Adobe is trialing a new service that might just fit your needs - Adobe's ""Protect an Adobe PDF File"" service:
What is the Protect an Adobe PDF File service?
Protect an Adobe PDF File is an online service that allows you to protect your Adobe PDF documents in powerful new ways. Once your PDF files have been protected using the Protect an Adobe PDF File service, you retain complete control over who can access your files and what actions the users of your documents may take. You even have the ability to modify allowable actions or revoke access to protected Adobe PDF files altogether after you have distributed your documents.
What exactly does Protect an Adobe PDF File allow me to do?
The Protect an Adobe PDF File service allows you to apply persistent usage rights settings to the PDF file itself. For example, you can:
Specify exactly who can open a protected Adobe PDF file, regardless of how the file is received, Restrict the types of actions that users can take (such as no printing, no copying, or no redlining and commenting), Specify a time period during which the file can be accessed by users, Revoke access to copies of the document even after you have distributed such copies, and Track events related to the copies you have distributed, such as when they were accessed, who accessed them, and more.
How much does the service cost?
The Protect an Adobe PDF File service is currently in beta. During the initial beta period, it is available at no extra cost to Create Adobe PDF Online subscribers. Subscription rates and other charges may be applied at the end of this period.
The Protect an Adobe PDF File service is also available now to trial users of Create Adobe PDF Online.
Looks like right now you have to be a part of Adobe's online PDF creation service."