First create the file with the relevant information

 

After creating and saving the document, click on File

 

Select Info

 

And then - Protect Document -> Encrypt with Password

 

Copy in the password

 

Note – As it says in the window, the file can no longer be opened without the password

 

At this point the file can be sent to the participants.

A participant will need to enter the password when opening the file. There will be no need to enter the password to save the document.