Thank you, Peter. On the computer (mac mini dual core) needing the upgrade of InDesign CS3, all the Adobe products (Photoshop CS5, Illustrator CS3, Bridge CS5, etc.) were installed separately, not using Creative Suite. On the I-Mac I have the CS5 Creative Suite. Question -- in order to be able to edit the same file back and forth, will I not need to have the same InDesign version? So, if I download InDesign CS6 (does it come separate from the Suite?) to the mac mini, will I not need it too on the I-Mac? Can permission be obtained to use the program on both my computers?
Lots of questions.
If I get permission to use the CS6 on both computers, will there be a problem with the I-Mac having CS5 in Creative Suite?
Yes, in your situation you will need the same version on both machines if you want a smooth exchange of files between them. InDesign is the same whether installed as part of a suite or as a standalone.
You can export IDML from CS6 and it should open on CS5, but if you use any CS6 new features they will be lost, and text will reflow due to differences in the text engines. C S5 files chould open in CS6, but you should also expect text to reflow if you touch a text frame.
I did not see "correct" below answer when I clicked on the forum. I appreciate your help, may need more later about IDML.