You can find it here:
If it is CS 5.5 or above, you need someone to open it in the version the script says and export an IDML representation from that. Another way would be to install a 30days version of CS6 or above (CC) and do it yourself.
In regards of the script showing a result for InDesign files higher than CS6:
CS7 = CC v9
CS8 = CC v10 = CC-2014 or CC2014.1
The two major causes of this error are a file that was not closed properly and left behind a lock file (.idlk) in the same folder, or attempting to open a file that is not really an InDesign file, perhaps that has had its extension changed. In your case it sounds more like the former, and that would be even more likely if you are saving to a network location. Look for the .idlk file and delete it. You can also try opening your file as a copy.
Thank you so much! I just tried all of your suggestions but It's still giving me the same error. I did have that .idlk file and I deleted it (emptied the trash and all). Still not working... Any more suggestions?
Thank you for replying! I just tried that Identify thing, were does it say the file version? I couldn't find it. The first words said PDF which freaked me out. I have been working on this file for months and its an .indd. Any suggestions?
The first words said PDF which freaked me out. I have been working on this file for months and its an .indd. Any suggestions?
Sounds like you've changed the extension on an exported PDF. Check for other copies of the .indd.