There are 3 ways to find a Plugin Alliance manual:
1. Webshop
Open the product page and scroll down to the Downloads section:
2. Plugin GUI
The manuals are installed automatically when you run the plugin installer. Open the plugin in your DAW. Click the question mark (?) at the bottom right corner and select Open Manual...
3. Manage Registered Plugins page
You can also download the manuals from your Manage Registered Plugins page.