The primary way to use ACD/Spectrus Processor for free is through time-limited official trials provided by 30-Day Desktop Trial Download a Free 30-Day Trial of the full desktop version of Spectrus Processor
If you only need to view spectra (not process): acd spectrus processor free download
Scam sites claim to offer cracked versions of Spectrus Processor. These often contain: The primary way to use ACD/Spectrus Processor for