You need the standaloneinstaller for Adobe Reader XI.
You can download it here: http://get.adobe.com/de/reader/enterprise/

1. Download the standaloneinstaller for Adobe Reader XI
   and put it to the CLIENT_DATA-directory on your Workbench.
   
2. Create new textfiles in the CLIENT_DATA-directory and fill them up with the scripts provided down there.
   You might want to edit some lines in order to fit your needs.
   
3. Ready the package and install it on your server.

[Actions]
Message "Installiert Adobe Reader XI"
SetLogLevel=6
Files_Copy_AdobeInstall
WinBatch_Install
WinBatch_CleanUp
 
[Files_Copy_AdobeInstall]
copy "%scriptpath%\*.*" "c:\adobeinstall\"
 
[WinBatch_Install]
c:\adobeinstall\AdobeReader.exe /sAll /msi /norestart ALLUSERS=1 EULA_ACCEPT=YES
 
[WinBatch_CleanUp]
rmdir /S /Q c:\adobeinstall\  

[Actions]
Message "Deinstalliere Adobe Reader XI"
WinBatch_autoit_delete /LetThemGo
WinBatch_uninstall
 
[WinBatch_autoit_delete]
%Scriptpath%\Remove.exe
 
[WinBatch_uninstall]
MsiExec.exe /I{AC76BA86-7AD7-1031-7B44-AB0000000001} 

Hint: this is an AutoIT3-Script

BlockInput(1)
Sleep (4000)
WinWaitActive("Adobe Reader XI (11.0.04) - Assistent", "Programm reparieren oder entfernen")
ControlClick("Adobe Reader XI (11.0.04) - Assistent", "&Adobe Reader XI (11.0.04) von Ihrem Computer entfernen.", "Button3")
ControlClick("Adobe Reader XI (11.0.04) - Assistent", "&Weiter >", "Button4")
WinWaitActive("Adobe Reader XI (11.0.04) - Assistent", "Installation abgeschlossen")
controlclick("Adobe Reader XI (11.0.04) - Assistent", "&Fertigstellen", "Button1")
BlockInput(0)