You can set security such that the file can be opened without a password, but a password is needed to edit the file. In Acrobat Pro XI, File > Properties > Security tab > set Security Method to Password Security then configure the restrictions as desired. Path may vary in other versions. It really just discourages editing though. Non-Adobe applications may or may not respect the restrictions, and any user with the ambition to do a google search can easily find out how to remove the restrictions completely. I am not an Indesign user so I do not know if the security-restricted PDF could be opened using Indesign.