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11.1. How to Encrypt and Password Protect Adobe PDF files
Last updated: Mon Jul 2026 09:31 AM (EDT)
Password-Protecting a PDF
You can add a password — and optionally encryption — to a PDF using Adobe Acrobat. For any sensitive or controlled document, use the desktop method below.
Using Adobe Acrobat (desktop) — recommended
- Select All Tools (called Tools in older versions), in the menu at the top of the page.
- Select Protect from the Tools list.
Alternatively, select Protect from the tools menu on the right side of the page:
- Select Protect using password (in the toolbar above the document).
- Fill out the prompt. To encrypt, expand Advanced Options and choose Encrypt with Password.
More detail on the available options: Choosing a security method for PDFs (Adobe).
Using Acrobat Reader (free online tool)
If you only have Acrobat Reader (not the full Acrobat app), Adobe offers a free online tool: Encrypt a PDF with password protection (Adobe Acrobat online).
⚠ Do not use the online tool for sensitive or controlled documents.
The online tool uploads your file to Adobe’s servers to add the password — so the document is exposed to a commercial cloud service. Never use it for CRL proprietary information, FOUO, CUI, or other controlled material. For those, use the desktop Acrobat method above. The online tool is only acceptable for non-sensitive files.
Adobe states that files are handled on its servers and deleted unless you sign in to save them — but that still means the file leaves your control, which is why it’s off-limits for anything controlled.
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