Hi Michal, 

Welcome to Box Community and I'm here to assist! 

You sure can password protect your file. All you have to do is create an open/public shared link. 

Meanwhile, to apply a password to a shared link:

1. Hover on the file or folder you want to share, then click Share. Box displays the Share window.


2. At the bottom of the Share window, confirm the scope is People with the link.  If the scope is any other value, you cannot add a password to the link.


3. Click Link Settings. Box displays the Shared Link Settings window.


4. In the Shared Link Settings window, check Require Password.


5. In the Enter a password field, type the password.


6. In the bottom of the Shared Link Settings window, click Save.

Hope it helps!