1. Make your pdf files readily available on your PC desktop.
2. Go to IW52, Click on GOS icon, Create... --> Create Attachment.
You will get a file select Dialog box, refer to your desktop file and attach. You can attach number of files this way. If you want to see the files you've attached, click on the Attachment list shown below Create.. in the above picture. You will get the list of all files attached. You can choose anyone and view.
KJogeswaraRao