Installing Adobe Reader without granting full administrative privileges
The 'Install Adobe Acrobat Reader DC.app' you downloaded is an online installer.

This means that the installer downloads Adobe Reader when you run the installer, such that the installer always installs the latest version, even if you run an older installer. This is why the installer is only ~2 MB, which is nowhere near enough to store Adobe Reader within, even compressed. Thus, there's no Adobe Reader inside that you can extract.

What you actually want is the offline installer, available to download from the Enterprise site:


https://get.adobe.com/reader/enterprise/


Select the version of OS X and your language, and you will be able to download the full installer of over 100 MB. Inside is your standard pkg that you can extract.