As you mentioned a free download, I'll assume you're looking for a downloadable software or tool. Here's a fictional download page:

: If you cannot find the password and don't need the current program, you can perform a Full Memory Clear . This resets the unit to factory defaults but erases the program.

In most jurisdictions, circumventing access controls on equipment you don’t own or without explicit permission violates computer fraud laws. Even if you own the PLC, reverse‑engineering tools may breach software license agreements.

: Some manufacturers offer official software tools designed for configuration, backup, and recovery purposes, which might include password resetting capabilities.