Appian Documentation for older releases

Hello,

I know there are older posts for this but since links are not working am posting again.
I am looking for information regarding the APPIAN update since version 17.
Is there a way to access old information (pdfs, or working links).

If anyone kept records for that I would appreciate it if he/she could share it.

The company I work hadn't update it and now that it needs update no information is found.
They spoke with the APPIAN support for over a month and no result [emoticon:ca08b2c27c2f40e993e89508acf29e0b]

Thanks in advance.