To password protect a PDF in Acrobat, choose All tools, Protect a PDF, then Protect with password, pick Viewing or Editing, type the password twice and select Apply. On a Mac, open it in Preview, choose File then Export, click Permissions and tick Require Password To Open Document.
Emailing a PDF with a client's details, a contract or a medical form is fine until it lands in the wrong inbox. A password doesn't make a file untouchable, but it stops casual snooping and it's quick to add. Here's how in Acrobat and in Preview on a Mac, and the difference between the two kinds of password that confuses almost everyone.
Password protect a PDF in Adobe Acrobat
- Open the PDF and select All tools, then Protect a PDF.
- In the left pane select Protect with password.
- In the dialog box choose whether the password is for Viewing or Editing.
- Type the password, then type it again to confirm.
- Select Apply and save the file.
There's also an advanced option that lets you encrypt the PDF using a password or a certificate. For most people the simple route is enough, but it's useful to know the choice exists if your organisation has rules about how files are protected.
The two kinds of password
Adobe's guide describes two different passwords, and mixing them up is the usual cause of a protected file that doesn't behave as expected.
| Password | What it controls | Use it when |
|---|---|---|
| Document Open Password | Who can open and read the PDF | You don't want anyone without the password to see the contents |
| Permissions Password | Who can change security settings, or print and edit | Anyone can read it, but you don't want it altered or printed |
You can use one, or both. A brochure you want customers to read but not edit needs only a permissions password. A file of personal details needs an open password. If you set a Viewing password and nothing else, anyone who has it can still do what the permissions allow.
When a certificate is a better choice
Adobe also offers certificate security, and its guide lists the advantages over a plain password: it encrypts documents for specific recipients, gives different people or groups their own access rights, and lets the document's creator be notified when the PDF is opened. If you send confidential files to the same few people every week, ask whoever manages your IT about it. If you send one file once, a password is simpler.
Password protect a PDF on a Mac with Preview
- Open the PDF in Preview and choose File, then Export.
- If you want a protected copy and an untouched original, type a new name for the file.
- Click the Permissions button.
- Select Require Password To Open Document, enter a password and retype it.
- Below that, choose which actions need the owner password: leave a tickbox selected to allow printing or changes without it, or deselect it to require it. Enter and retype an owner password.
- Click Apply, then Save.
Apple adds that changes take effect the next time the PDF is opened, so test it: close the file and reopen it before you attach it to anything. If you want to adjust the protection later, choose File, then Edit Permissions.
Test it before you send it
- Close the file and reopen it. It should ask for the password.
- Check you can read the file you protected. Typos in a password you typed once are the main cause of locked-out owners.
- Send the password by a different route from the file, such as a text message rather than the same email.
- Keep an unprotected original somewhere safe. Assume a forgotten password can't be recovered, so write it down somewhere safe.
Share the file safely
When the PDF is going to one person, attach it to a normal email and send the password in a message on a different app. If it's going to a group, think about whether everyone really needs the same password, because the more people who know it, the less it protects. For files that change hands often, a shared folder with its own access controls is often tidier than passing protected attachments around.
What a password doesn't do
Be realistic about what you've bought. A password stops people opening or changing the file without it. It doesn't stop someone who has the password from sharing it, and it doesn't hide information you wouldn't want anyone to read in the first place. If a document contains something you need removed rather than locked, Adobe describes two other tools in Acrobat Pro: redaction, which permanently removes sensitive information, and sanitizing, which strips out hidden data and metadata.
Want AI doing the heavy lifting in your marketing?
I build the systems that handle the boring 80 percent, so you get your week back. Done properly, with the human kept in.
Good password habits help too. A strong, unique password for each sensitive file is easier to manage with a password manager, and my comparison of Bitwarden and 1Password is a good place to start. I've also covered what to check before choosing 1Password.
My verdict
Use Protect with password in Acrobat, or Export with Permissions in Preview, and decide first whether you're locking the front door (an open password) or the editing and printing controls (a permissions password). Test the file before it goes, send the password separately and keep an unprotected original.
Frequently asked questions
How do I password protect a PDF?
In Acrobat choose All tools, Protect a PDF, Protect with password, pick Viewing or Editing, enter the password twice and select Apply. On a Mac use File, Export, Permissions in Preview.
What's the difference between an open password and a permissions password?
An open password is needed to open the PDF. A permissions password is needed to change security settings or do restricted things such as printing and editing.
Can I password protect a PDF on a Mac without Acrobat?
Yes. In Preview choose File, Export, click Permissions and select Require Password To Open Document.
Can I keep the original unprotected?
Yes. In Preview, type a new name in the Export dialog to create a protected copy and leave the original alone.
When does the password take effect?
In Preview, Apple says changes take effect the next time the PDF is opened, so close and reopen the file to test it.
