Is it possible to create a password for a file on Adobe Reader X?
As other's have said, you cannot password protect with Adobe Reader. However, programs such as PrimoPDF (Freeware) can do this for you.
See this video..
A lot depends on what version of Acrobat you are using.
On Acrobat 8 Pro, you select File->Properties and under Security tab,
select Security Method from dropdown list to be "Password Security." A new
dialog opens that allows you to determine the options as to what will be
secure regarding the document: does it require a password just to open it?
or can it be opened, but no changes/copying/printing allowed. You set all that up, enter the password and confirm that entry, and it's done when you save that document.
With other (earlier) versions of Acrobat, the command for setting passord is still under the File menu (it might read Document Properties or Document Security) and the interface is basically the same with respect to setting options.