PDF guides5 min read
How to password protect a PDF
Lock a PDF with a password before you send something private, and understand what that lock does and doesn't do.
PDFs have two kinds of protection, and they're not equally strong. An open password (sometimes called a user password) scrambles the file so nobody can read it without the password. Permissions (set with an owner password) leave the file readable but ask the reader's app not to allow printing, copying or editing.
Only the open password is real protection. Permissions rely on the reader's app choosing to respect them, and plenty of apps don't. Think of permissions as a polite request, not a lock.
There's also an order to things. Once a PDF is encrypted, most other tools can't open it. So add the password last, after you've finished merging, numbering and any other edits.
And be realistic about what a password does. It decides who can open the file. Once the right person opens it, they can take a screenshot, retype it, or forward it along with the password. A password keeps the file safe on the way there. It won't stop someone you trusted from sharing it. It works best when you send the password separately from the file.
When you might need this
- You want to keep private information away from casual eyes.
- You're about to email a confidential document.
- You want to limit printing, copying or editing of a private PDF.
- Your workplace requires encryption on files with personal data.
- You want to make it clear the document isn't for passing around.
How to do it
- Finish all your other edits first. An encrypted PDF can't be merged, split or compressed until it's unlocked.
- Open Protect PDF.
- Choose the PDF you want to protect.
- Pick which actions to allow: printing, copying, editing and so on.
- If you want, enter a strong open password. Then protect the file and download it.
- Open the downloaded file and test the password and permissions before you send it.
Free, with no account. Open it in a new tab and follow along.
Open Protect PDFTips
- Use a password you don't use anywhere else. A few random words strung together is both stronger and easier to read out over the phone than a short jumble of symbols.
- Send the password a different way from the file, like a text message or a phone call. A password in the same email as the attachment protects nothing.
- Leave the open password empty if you only want permission limits.
- Save the password somewhere safe, ideally in a password manager.
- Remember that anyone who can read the document can take a screenshot. A password controls who opens it, not what they do next.
Common mistakes
- Emailing the password along with the file.
- Treating permission limits as if they were encryption. Many PDF readers ignore them.
- Adding the password before merging or numbering, and then finding no other tool can open the file.
- Using a password you can't recover, with no copy of it anywhere.
- Assuming a password stops the recipient from sharing the content.
How this compares to Smallpdf, iLovePDF and Adobe
To protect a PDF on Smallpdf, iLovePDF or Adobe's online tools, you upload the confidential file and, if you set an open password, type that password into their website. These are well-known companies and they delete files on a schedule. Still, it's a bit odd to hand the private thing to someone else in order to make it private.
The usual limits apply too. All three limit the free plan, cap the upload size and push you toward an account. That gets in the way when you have a batch of documents to lock in one sitting.
Here, the file is protected in your browser. You don't need an account, there's no limit on how many files you protect, and no upgrade screen appears halfway through.
| Criterion | Smallpdf | iLovePDF | Adobe Acrobat online | Easy File Tools |
|---|---|---|---|---|
| Where your file is processed | On their servers, after you upload it | On their servers, after you upload it | In Adobe's cloud, after you upload it | In your browser, on your own device |
| Account or sign-in | Asked for early, and needed once you pass the free allowance | Optional for small jobs, needed for bigger ones | Most online tools need an Adobe ID | Never needed |
| Usage limits | A few free tasks, then an upgrade prompt | Daily task and file limits on the free plan | The free web tools are mostly a preview of the paid plan | No task counters and no daily limits |
| File size ceiling | The free plan limits upload size | The free plan limits upload size | Cloud upload limits apply | We don't set one. Your device's memory is the practical limit |
| Works without a connection | No, their server does the work | No, their server does the work | No, the cloud does the work | Yes for the browser tools, once the page has loaded |
| Cost | Paid subscription for full access | Paid subscription for full access | Paid Acrobat subscription for full access | Free. Every tool is open to everyone |
Other services change their plans and limits often, so treat this as a rough picture and not a price list. Check their websites for the current details.
Frequently asked questions
- Do I have to set an open password?
- No. It's optional. Leave it empty if you only want to limit things like printing, copying or editing.
- Can I get back into a PDF if I forget the password?
- Usually not. Save the password in a password manager before you send the file.
- Should I email the password with the PDF?
- No. Send it another way, especially if the document is sensitive.
- What's the difference between an open password and permissions?
- An open password encrypts the file, so it can't be read without the password. Permissions leave the file readable and rely on the reader's app to follow the limits.
- Can someone still copy text from a restricted PDF?
- Possibly. Permission limits are only a request, and not every app follows them. An open password is the only real control over who can read it.
- Do I need an account to protect a PDF?
- No. There's no sign-in and no limit on how many files you protect, so you can do a whole batch at once.