PDF files are portable and PDF is quite the standard format for professional documents. These files can be easily shared and accessed. But what's even cooler is that PDF files can be password-protected. You can lock down the files with a password just as easily on a Mac OS X.
You can password protect or encrypt the documents using two ways; one by directly printing the encrypted PDF or two by encrypting the PDF via the Preview app. On both counts, we're talking about:
Add Password or Encrypt your PDF from Browser
Step 1: In your web browser, open the document you want to print. Use the keystroke Command + P to open the printing dialog box.
Step 2: Right at the bottom of the dialog box, where it says PDF, select the option: Save as PDF.
Step 3: Click on Security Options
Step 4: Check Require Password to open document and type a password.
Step 5: Once you've verified the password, click OK. Optionally, you can also add a password to copy and print the document. More security.
Step 6: Save the document as a new PDF file.
Add Password using Preview:
Step 1: Open the PDF file in Preview. (In most cases, Preview will be the default app that opens PDF files on your Mac.)
Step 2: Select File from menu bar and then choose: Export as PDF
Step 3: Click on Show Details from the dialog box.
Step 4: Check the option Encrypt
Step 5: Type in your password and choose a destination to save it in.