Creative suite --> win 11 stuck on trial

Even if you had a valid license, obsolete software isn't compatible with modern equipment and operating systems. Too much has changed.

MODERN OPTIONS:
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FREE Acrobat Reader -- view, comment, print & sign PDF.
https://acrobat.adobe.com/acrobat/pdf-reader.html

Paid Acrobat Pro DC -- the complete solution for creating and saving PDF.
https://acrobat.adobe.com/acrobat/acrobat-pro.html

Photoshop Elements or Premiere Elements (no subscription needed).
https://www.adobe.com/products/photoshop-elements.html

Creative Cloud Photography Plan (approx $10/month for 12 months). Includes the following:

• Photoshop CC and Photoshop on iPad
• Camera Raw
• Lightroom on desktop, mobile and the web
• Lightroom Classic
• Portfolio website + hosting
• Adobe Express (free starter plan)
• Bridge
• 20 GB cloud storage (upgradable to 1 TB).
• Free upgrades for paid subscribers

https://www.adobe.com/creativecloud/photography.html

Premium Adobe Express ($10/month). Mobile & web-based graphics & video apps for social media content creators.
https://helpx.adobe.com/express/using/express-overview.html

Creative Cloud Bundles & Single App Plans for mobile, web & desktops
https://www.adobe.com/creativecloud/plans.html

Make sure your computer meets the minimum CPU & GPU requirements. Most Creative Cloud apps work on:

• Windows 11 (64-bit) versions 23H2, 22H2; Windows 10 versions 22H2, 21H2;
• MacOS 14.7 (Sonoma), 13.6.7 (Ventura), 12.7.6 (Monterey).

- https://helpx.adobe.com/creative-cloud/system-requirements.html

Which CS version?

The activation servers for CS2,3,4 have been shut down.

if you saw an invalid serial number you either made an error when entering the number OR you have the wrong installer.  details:

assuming you're using a valid adobe serial number (6 groups of 4 numbers), 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 (correct) 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