SPX Encryption – Attachments could not be seen with Adobe XI
Some versions of Adobe Reader (8.1.7, 8.2, 9.0+) open PDFs with attached files slowly (few minutes) if „Enhanced Security“/“Protected Mode“ is turned on.After that few minutes attachments can be opened or saved again depending on security settings. This can happen when opening PDF in SPX-encrypted e-mails.
This page contains information on configuring attachments‘ security in Adobe Reader: http://www.adobe.com/devnet-docs/acrobatetk/tools/AppSec/attachments.html
Furthermore the user (or admin) can disable the „Protection Mode“ of Adobe Reader by un-checking this checkbox: Edit -> Preferences -> Security(Enhanced) -> Enable Protected Mode at startup.