1603 Error during updating adobe reader 11.0.18.

Actual failure is due to:

MSI (s) (94:C0) [11:51:22:904]: Product: Reader -- Error 1706.No valid source could be found for product Reader.  The Windows Installer cannot continue.

Error 1706.No valid source could be found for product Reader.  The Windows Installer cannot continue.

Most probably some base\RTM files that need to be updated are missing and you installed using AIP (because MSI filename is coming up as C:\Program Files (x86)\Adobe\Reader 11.0\Setup Files\{AC76BA86-7AD7-1033-7B44-AB0000000001}\Adobe-Reader-11-EN-1.0.msi). Now source AIP is missing and hence installer is unable to find RTM files. My conclusion is that you first installed using AIP and you're now trying to apply patch over it which is an unsupported scenario. Do you remember using "msiexec /a ".

If you installed using AIP once then you must always use AIP to patch the product.