I only see a trial version of Acrobat XI Pro.
Unfortunately there is no trial version of Acrobat XI Standard, just Acrobat XI Pro. At least I could not find one. I did download the Pro version, and entered my serial number, but the installation screen said it was not a valid number ... and I just purchased/downloaded the Standard version less than a month ago.
Good question Pat. I purchased the XI Standard as an add-on when I purchased a new Dell laptop. When I went to install the S/W, Dell tossed me over to the Adobe website, where I had to create a profile, and only gave me the option to install the S/W. I had no option to download, and then install.