Encrypt a PDF Encrypting a PDF can help keep the document secure when sending it through e-mail or other means. Follow these instructions to encrypt a single PDF document. 1. With the document open in Adobe, navigate to All tools and click Protect a PDF 2. Under Advanced Options, click Encrypt with Password 3. A pop-up will appear, click Yes 4. Check the box next to “Require a password to open the document.” Choose a secure password. Click Ok. 5. A pop-up will appear, confirm the password and click Ok. 6. Another pop-up will appear, click Ok. 7. Save the document. The document will now be encrypted with a password. Anyone who tries to open this document will need the password to open it.