you have 3 ways to recover a serial number that you once had:
1. if you purchased from or registered with adobe (automatically done with cs6):,
a. you can check your account, https://accounts.adobe.com
b. you can check with adobe support* (be prepared to give the email address used when registering purchasing)
2. 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/
3. http://helpx.adobe.com/x-productkb/global/find-serial-number.html
*
using a browser that allows popups and cookies, contact adobe support during pst business hours by clicking here and, when available, click 'chat', http://helpx.adobe.com/x-productkb/global/service-ccm.html
[ moved from Creative Suites to Downloading, Installing, Setting Up]