I created this howto a while ago.
How to password protect files by saving them as PDF's using Open Office.
Note: The file must be in Open Document or a format that Openoffice can read. And then:
- Using Openoffice. Open the file you want to password protect.
- Click File ==> Export as PDF
- On the PDF Options box that appears. Click the Security Tab and click the "Set open password"
button. - Enter a password and click OK.
- Then click Export to save the file as a password protected PDF.
And once more with pictures: How To Create Password Protected PDF Files Using OpenOffice
One can first install "pdftk" cli and the do this from terminal :
pdftk source.pdf output protected.pdf user_pw PROMPT
One can also replace PROMPT with his/her own password like:
pdftk source.pdf output protected.pdf user_pw 123456
If some one is using Ubuntu or Fedora he/she can use nautilus actions tool to add an entry in context menu to lock pdf.