A family of Microsoft word processing software products for creating web, email, and print documents.
In Word, you can set a password for opening a document via File > Info > Protect Document > Encrypt with Password.
When you save as PDF, you can use the "Encrypt document with a password" option in the PDF Options dialog box. In the Save As dialog box (press F12 or Fn+F12 on some keyboards), change the file format to PDF and then click Options. See screen shot below.