You may use the following method to install Adobe Reader XI silently and accept the End User License Agreement (EULA):

msiexec.exe /i AcroRead.msi EULA_ACCEPT=YES /qn

Additionally, you may use the Adobe Customization Wizard XI to customize the installation of Adobe Reader XI. Please keep in mind that the Adobe Customization Wizard must match the version of Adobe Reader that you are installing.

Lastly, in order to get the .msi file you must first install the Adobe Reader XI application then navigate to the “C:\ProgramData\Adobe\Setup\{AC76BA86-7AD7-1033-7B44-AB0000000001}\” directory to retrieve it. This directory also contains the Setup.ini file which is needed in order to save any settings, using the Adobe Customization Wizard XI, to the .msi file.