I've just tested Adobe Reader X in Windows 7, and for me, Window Snapping works, and it has the titlebar button. Could you send me your troubleshooting info while Adobe Reader X is open? Here are the steps:

• Open the DisplayFusion Settings > Troubleshooting tab
• Click the Copy to Clipboard button
• Open Notepad, paste the text, and save the file
• Reply with the text file attached