This sounds like more of a client issue than a server issue. Start trying to have only one Acrobat version on the client and ensure the client printer drivers are installed correctly and can print sample PDF files from Acrobat fine. For PDF printing directly from R12, please review the PASTA documentation:
11i-12 How to Setup Pasta Quickly and Effectively (Doc ID 356501.1)
How To Print Concurrent Requests in PDF Format (Doc ID 333504.1)
YES this is client end issue.
On simple adobe reader 11 it works fine.