Hi,To open attached PDF files in a new window in Odoo 16, you can customize the behavior using JavaScript. Below is a step-by-step guide on how to achieve this:

1. Override JavaScript Functionality: In Odoo 16, the JavaScript functionality responsible for opening attached PDF files is handled by "ir.actions.report handlers". You'll need to override this registry.
2. Modify the JavaScript Code: Within the JavaScript code, locate the function or event handler that handles the opening of attached PDF files. Modify this code to ensure that PDF files are opened in a new window/tab.

3. Use window.open(): Replace the existing code that opens the PDF files with a call to the window.open() function. Pass the URL of the PDF file as a parameter to window.open().

Alternatively, you can explore third-party modules available in the Odoo app store related to handling attached PDF files preview.

Hope it helps