I just downloaded the trial version of InDesign CS6. But I can't open files saved with CS8.1 ... what should I do now?
CS8.1 would really be CC 2014.
As Peter said, you would want to download the trial for InDesign CC 2014. Or get the person(s) who created them in CC 2014 to save as IDML so you can open them in InDesign CS6.
Retrieving data ...