Protect a PDF with Passwords and Permissions
How do you password-protect a PDF so only the right people can open it?
Protect a PDF with password and permission settings. A user password controls opening the file, while an owner password controls changes to its permissions. Choose an encryption option compatible with the recipients’ PDF reader and keep the password separately from the document. Check that the exported PDF opens with the intended password before distributing it.
Cost: Free to use. File size and usage limits apply.
How to protect a PDF
Upload one PDF
Click Choose PDF, drop the file onto the preview, or pick it from Uploads, where results from other tools on this site also appear. One PDF of up to 200 MB per job. The file must not be protected already.
Set the owner password
Enter it in Owner password. It is the only required field and gives full control over the file later, so type it carefully and store it somewhere safe.
Add an open password if needed
Fill in User password (optional) when people should need a password just to view the document. Leave it empty if anyone may open the file and you only want to restrict printing, copying or editing.
Choose encryption and permissions
Keep AES with 256 bit unless a recipient uses very old software. Then pick Restrict all, Allow print or Allow all under Permissions.
Protect, download and test
Click Protect PDF, then Download protected PDF. Open the download in the reader your recipients use and check that it asks for the password and blocks what you restricted before you send it.
Passwords, encryption and permissions explained
The Settings card has five fields. Defaults are AES, 256 bit and Allow print.
- Owner password
- Opening the file with this password grants every right, including printing, editing and removing the protection. Make it different from the user password: if both are the same, everyone who can open the file also gets full rights and your permission choice has no effect.
- User password (optional)
- When set, PDF readers ask for it before showing any page, and the content can't be decrypted without it. When empty, the file opens for everyone without a prompt and only the permission restrictions apply.
- Encryption mode
- AES is the default and the current standard. RC4 is an older cipher with known weaknesses, kept for compatibility with very old readers. Choose it only if a recipient can't open AES files.
- Key length
- With AES you can pick 128 bit or 256 bit. With RC4 you get 40 bit or 128 bit; switching from AES 256-bit to RC4 selects 128 bit. AES 256-bit is supported from Acrobat 9; AES 128-bit is also supported by Acrobat 7 and 8. Check the reader your recipient uses. Avoid 40 bit: the key is short enough to be brute-forced directly, whatever password you chose.
- Permissions
- Allow print allows printing at full quality and blocks copying text and images, editing, comments, form filling and page assembly. Restrict all blocks printing as well. Allow all sets no restrictions, which fits when you only want the open password. For other combinations, such as allowing form filling but not editing, use PDF Permissions.
- Password characters
- For the widest compatibility with older PDF readers, use unaccented letters, digits and common punctuation. Spaces at the start or end of a password are removed before encryption.
What the passwords can and can't protect
The user password, often called the open password, is the real barrier: without it, a reader can't decrypt the pages. The owner password, also called the permissions password, unlocks full rights; everyone else only gets what the permissions allow.
Permission restrictions are flags stored in the file. Adobe Acrobat and many other readers respect them, but some viewers and editing programs ignore them and can print or copy from any PDF they can open. If your file opens without a password, treat the restrictions as a deterrent, not as protection for confidential content.
With AES, the weak point is the password, not the cipher. As a rule of thumb, use at least 12 characters, don't reuse a password from another account, and share it through a different channel than the file, for example by phone when the PDF goes out by email.
Recommended combinations
Confidential document for specific people
User password plus a different owner password, AES 256 bit, Allow print or Restrict all. Only people who know the user password can read the content.
Handout that anyone may read
No user password, Allow print. Everyone can open and print it; readers that respect permissions block copying and editing.
Marked and locked draft
Add a visible CONFIDENTIAL stamp with Watermark PDF first, then select the watermarked result under Uploads and protect it. Make protection the last step, after all other edits, so none of them has to deal with a password.
Formats and limits
- Input format
- PDF, 1 file per job
- Maximum file size
- 200 MB
- Already protected PDFs
- Not supported. PDFs that already need a password or carry permission restrictions fail; remove the existing protection first.
- Output format
- PDF with the same pages and content, saved as PDF 1.7.
- Metadata
- Title and author are kept. The producer entry is set to pdfcpu; the creation and modification dates are set to the time of processing.
- Digital signatures
- The file is rewritten, so existing signatures will show as invalid.
- Processing
- On our servers with the pdfcpu PDF library. A job can run for up to 15 minutes.
- Watermark
- None
- Storage
- Uploads and results are deleted automatically after 48 hours for guests and after 30 days for free accounts. Paid plans can keep files longer.
Frequently asked questions
Why does my protected PDF open without asking for a password?
User password (optional) was empty, so the file has restrictions but no open password. Select your unprotected original under Uploads and run the tool again with a user password.
Why did protecting my PDF fail?
Use an intact PDF without existing encryption. A file can already have password protection even when it opens freely and only restricts printing or copying. Remove that protection with Unlock PDF, using a valid password, then protect the unlocked copy. Re-save or repair a damaged PDF before processing it.
Can I recover a forgotten password?
No. There is no password recovery here, and a file with an AES open password can't be read without it. If you still know the owner password, Unlock PDF can remove the protection with it. Keep your unprotected original until you have tested the new passwords.
Are my PDF and passwords sent to your server?
Yes. Encryption runs on our server, so the PDF and both passwords are transmitted with the job; no external service is involved. Files are deleted automatically as described under Storage above. Use passwords you don't use anywhere else.
Does protection reduce quality or make the file bigger?
Applying a password does not resample text, images or fonts. The PDF is rewritten and encrypted, so its byte size can change according to the original document and structure; the difference is not a fixed overhead. To reduce its size, try Compress PDF before protection and compare the actual files.