CS6 is over a decade old and was discontinued in 2014. It is generally incompatible with modern operating systems like Windows 11 or the latest macOS versions. Official Adobe Options
A: There is none. No free software can natively edit InDesign files. You can use IDMarkz (paid) to convert INDD to Scribus format, or ask colleagues to export to IDML. Adobe InDesign CS6 Portable Free Download