Two kinds of PDF password
Most PDF tools offer two passwords, and they do different jobs:
- A password to open. Nobody can see the pages without it. This is what most people mean by a password-protected PDF.
- A permissions or owner password. The PDF opens for anyone, but printing, editing or copying text needs the second password.
The permissions kind is weaker than it sounds. LibreOffice's own help notes that these restrictions "will be observed only by PDF readers compliant with the version 1.5 of the format", so "in older PDF readers, the restrictions may have no effect" (LibreOffice Help). For anything private, set the password to open.
Adobe Acrobat (paid)
The desktop Acrobat app, the paid version rather than the free Reader, sets both kinds of password. Adobe's steps (Adobe Help):
- Select All tools > Protect a PDF.
- Under Advanced options, select Encrypt with Password, then Yes.
- Select Require a password to open the document and type it in the Document Open Password field.
- Retype it, confirm the security message, and save the PDF.
The same screen sets a permissions password to limit printing, editing and copying. Adobe also runs a Protect PDF page in the browser, which it titles as free. The PDF is uploaded to Adobe's servers to do it.
Preview on a Mac (free)
Preview comes with every Mac and can add both passwords (Apple Support):
- Open the PDF in Preview and choose File > Export.
- To keep an unlocked original, type a new name for the copy.
- Click Permissions and select Require Password To Open Document, then enter and retype the password.
- Enter an owner password as well, then click Apply and Save.
Apple notes that changes take effect the next time the PDF is opened.
Microsoft Word on Windows
When the PDF starts life as a Word document, Word can lock it as it saves (Microsoft Support):
- Choose File > Save As or Save a Copy, and pick PDF as the type.
- Select Options.
- Tick Encrypt the document with a password and select OK.
- Type the password twice in the Encrypt PDF Document box, then save.
Microsoft's steps for Word on a Mac do not include this option, so on a Mac, save the PDF first and lock it in Preview.
LibreOffice (free)
LibreOffice is a free office suite. Choose File > Export As > Export as PDF, open the Security tab and click Set passwords. There is a field for a password to view the PDF and an optional one for editing and printing (LibreOffice Help).
Before sending a locked PDF
- Keep the password somewhere safe. Microsoft is blunt about Word documents: "If you lose or forget your document password, Word won't be able to recover it for you" (Microsoft Support). Keep an unlocked original too.
- Test the locked copy. Open it once before sending, ideally on a second device, to check that it asks for the password and that the right one opens it.
- Send the password a different way. A password in the same email as the PDF protects nothing once that email is forwarded. Send it by text, or use a one-time password link that deletes itself after it is read.
A password on the file, or a password on a link
There is a second way to lock a PDF: leave the file alone and put the password on the link that serves it. The two behave differently.
| Password on the PDF | Password on a Snapy.host link | |
|---|---|---|
| Where it lives | Inside the file | On the web address |
| After a download | Still locked | An ordinary, unlocked PDF |
| Works offline | Yes | No, it needs the web |
| Change or remove it later | Only by sending a new file | Any time, from the link's settings |
| Expire it after a date | No | Yes, after 1, 7 or 30 days, free |
| Stop downloads | No | View-only, free |
| See if it was opened | No | Yes, with a free email on the first open |
To be plain about it: Snapy.host does not encrypt the PDF. The password guards the link, and the PDF is only shown after the right password is typed. A page that tries to embed the file elsewhere gets the password prompt too. But anyone who unlocks the link and downloads a copy holds a normal PDF. View-only removes the download button, which cuts down on that, but a reader can still photograph a screen, so treat it as friction, not a lock.
Which one to use
- The file will be stored, forwarded or opened offline, such as a payslip, a medical record or a tax form: put the password on the PDF itself.
- The file should be read, not kept, such as a proposal, a price list or a draft: a password on a PDF link, with view-only and an expiry, does more. It can be changed after sending and shows whether the PDF was opened.
To put a password on a link, drop the PDF into secure document sharing, up to 150MB, and turn on a password in the link's settings. Password, expiry and view-only are all free. No sign-up: the first upload asks for a one-time code sent to the sender's email, to keep out spam. The person who opens the link needs no account.