I purchased CS2 back in 2011. I use Photoshop, Acrobat and iIllustrator, but have never cracked open InDesign. And never had the need to upgrade to newer versions. (Semi retired) So someone sends me a file actually created in InDesign CS2 to edit and I think I'm good because I did load it onto my computer. But then I get a message saying I can't open the file until I upgrade the plugins. And of course Adobe doesn't keep them available for download any longer. Am not in a position to shell out a bunch of money upgrading to newer versions. Is there any way to get these plugins?
THis means that these files were created in a later version of InDesign. To open them you have to buy a later version of InDesign, with InDesign CS2 (this was not available in 2011! but many years before!) you have bad luck.
You could try a 30 day trial of the present version.
2011? CS2 was released in 2003 I believe and has not been available through legitimate channels for about 10 years.
There is no way to save a file from anything other than CS3 back to CS2.