Software which will not run on your computer will not appear as available for download in the AAM.
Adobe Premiere Pro, After Effects and Encore are all 64 bit only meaning they will only run on 64 bit operating systems.
http://www.adobe.com/au/products/premiere/faq.html#64bit-support
Is your operating system 32 bit? e.g. Windows 7 32 bit? If so, you will not be able to download or install Premiere Pro. You will have to upgrade to a 64 bit computer.