you can install the latest and 1 version prior versions using the cc desktop app. you must have a subscription because previous versions are not available with trials. other versions are revealed after clicking file preferences>apps>tick show older apps (at panel bottom).
for versions prior to cc 2020, use prodesign tools.com*.
for versions between cc 2019 and one previous version, contact adobe support for links.**
most adobe download links are available from prodesigntools.com. https://prodesigntools.com/adobe-direct-download-links.html
follow the directions (esp, step 1)
save the install file. it may not remain online.
thank jim @ prodesigntools.com
use a browser that allows popups and cookies and contact adobe support by clicking here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human
p.s you can also use phone (but chat is usually quicker), https://helpx.adobe.com/contact/phone.html
p.p.s. you can also use twitter to tweet @AdobeCare
p.p.p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative. ie, double check for an employee badge if contacted in the forums and look for an adobe.com domain in the email address if you click reply to an email. then check again and be very suspicious. any other method of contacting (or offering to contact you) is almost certainly a scam, https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-com...