Adobe Acrobat (DC 32 Bit) Serial Number Invalid

you can check your account (if you purchased from or registered with adobe), https://accounts.adobe.com

or if your adobe program is installed on another computer you can recover its serial number from that computer, (win:) http://www.belarc.com/free_download.html, (mac:)  https://mac-product-key-finder.com/

otherwise, http://helpx.adobe.com/x-productkb/global/find-serial-number.html

and you may be using a valid serial number and still see that message if you have a mismatch between your installation file and serial number.  ie, you can have a valid serial number, but if it's for program A and your installation file is for program B, you will see an invalid serial number message.

common mismatches are language/region (eg, serial number is for western europe and installation file is eastern europe), platform (eg, serial number is for a mac and installation file is win), license type (eg, education vs enterprise vs individual).

and one of the most common is using a program installation file with a suite's serial number. eg, using a cs6 suite serial number with a photoshop cs6 installation file.  that won't work even though photoshop is included in that suite.  you must use the suite's installation file (and you can choose to only install one program from the suite).

here's official info about that error,  http://helpx.adobe.com/creative-suite/kb/error-serial-number-valid-product.html