[All articles](https://linkinseconds.com/blog) # How to password-protect a PDF for free (Mac, Windows, phone) [Sunny](https://linkinseconds.com/about#who-runs-this)·September 14, 2026· 8 min read [#pdfs](https://linkinseconds.com/blog/topic/pdfs-and-documents)[#secure](https://linkinseconds.com/blog/topic/secure-sharing)#security#password#protect Lock it in 30 seconds Mac · Windows · phone contract.pdf Live lisview.com/locked Adobe would like this to require a subscription. It doesn't. Every mainstream operating system can already encrypt a PDF with software you have, and one free desktop app does it with stronger encryption than Acrobat's default. Here are the four routes, what encryption each actually gives you, and, more usefully, the two ways a PDF password quietly fails to protect anything. ## Which method, in one table | Method | Platform | Encryption | Cost | | Preview | macOS | AES-128 | Free, already installed | | Microsoft Word | Windows / Mac | AES-128 | Free if you have Office | | LibreOffice | Windows / Mac / Linux | AES-256 | Free, ~350 MB download | | Online tools | Any | AES-128 or 256 | Free, you upload the document | ## Method 1: macOS Preview Try it while you are reading Upload a file and get a clean, trackable link with a QR code. Free, and no account for whoever opens it. [Create a link](https://linkinseconds.com/) The fastest route if you have a Mac, with nothing to install. The one thing people miss is that this lives under **Export**, not Save. The Save dialog has no encryption option at all, which is why so many people conclude Preview can't do it. - **Open the PDF in Preview.** Double-click the file on any Mac, Preview is the default PDF app and needs nothing installed. - **Choose File → Export as PDF.** Use Export, not Save. The Save dialog has no encryption option; Export is where the permissions live. - **Click Permissions and set a password.** Tick “Require password to open document” and type your password twice. You can also separately restrict printing and copying. - **Save as a new file, then verify.** Keep the unlocked original under a different name. Close the new file, reopen it, and confirm it actually asks for the password before you send it anywhere. ## Method 2: Microsoft Word Works when you still have the source document rather than only a PDF. Go to **File → Save As**, pick PDF as the format, then click **Options** and tick **Encrypt the document with a password**. You get AES-128. The limitation is real: Word can only do this while _producing_ a PDF. If someone sent you a finished PDF, Word can't encrypt it without converting it first, which will rearrange your layout. Use Preview or LibreOffice for those. ## Method 3: LibreOffice (the strongest free option) Free, open source, runs on everything, and recent versions do **AES-256**, stronger than what Preview or Word produce. Open the PDF, choose **File → Export as PDF**, open the **Security** tab, click **Set Passwords**, and set an open password. Worth the download if you do this regularly, or if a client has specified 256-bit encryption. For a one-off on a Mac, Preview is quicker and AES-128 is not a weak link. ## Method 4: Online tools (read this first) They work, and they're convenient. But look at what the transaction involves: **you upload an unencrypted confidential document to someone else's server** so that it can be encrypted there, and you hand that server your password as well. Reputable services delete files after an hour and say so. You are still trusting a third party with exactly the document you decided was too sensitive to send in the clear. The offline methods above are free and take the same two minutes. If the document is sensitive enough to encrypt, it is sensitive enough not to upload to a stranger first. ## The two ways a PDF password fails you ### 1. You set the wrong kind of password PDFs support _two_ passwords and they are not remotely equivalent: - **Open password (user password)**: the file is genuinely encrypted. Without the password there is nothing readable on disk. This is the one you want. - **Permissions password (owner password)**: the file is _not_ encrypted. It merely carries a flag asking viewers not to allow printing or copying. Compliant readers honour it; free tools strip it in seconds. People set the second one, see “protected” in the dialog, and believe the document is secure. It isn't. If your PDF opens without prompting you for anything, it has no real protection at all. If what you actually want is to let people read a file without saving a copy, a [view-only link](https://linkinseconds.com/view-only-file-sharing) enforces that server-side, which a permissions flag never can. ### 2. The password travels with the file The more common failure, and it has nothing to do with cryptography. You attach the encrypted PDF and type the password in the same email. Anyone who intercepts the message, or who the message is forwarded to, now has both halves. Send the password by a different channel: a text, a call, anything that isn't the thread carrying the file. And plan for what happens next: your recipient will lose it. A PDF password can't be reset, rotated, or revoked. If it leaks, your only option is to re-encrypt the document with a new password and re-send it to everyone. ## When a link password is the better tool Encrypting the file protects the _file_, everywhere it goes, forever. That's exactly right for an archive, a document crossing an untrusted network, or anything with a compliance requirement attached. It's often the wrong tool for _sharing_, though, because the protection is welded to a copy you no longer control. If you instead [turn the PDF into a shareable link](https://linkinseconds.com/pdf-to-link-converter) and put the password on the _link_, you keep the controls in your hands: | | Password on the file | Password on the link | | Change the password later | No, re-encrypt and re-send | Yes, instantly | | Revoke access after sending | No | Yes, disable the link | | See whether it was opened | No | Yes | | Add an expiry date | No | Yes | | Update the document itself | No, new file, new send | Yes, same link, new file | | Protects an offline copy | Yes | No | We covered that route in detail in [how to password-protect a file you share by link](https://linkinseconds.com/blog/password-protect-a-file-you-share). And the two aren't exclusive: for something genuinely sensitive, encrypt the file _and_ [share it as a password-protected link](https://linkinseconds.com/share-files-online) with an expiry date, so a leaked copy is still encrypted and the link stops working regardless. ## Quick answers ### How do I password-protect a PDF for free? On a Mac, open the PDF in Preview and choose File → Export as PDF → Permissions, then set a password. On Windows, open the document in Microsoft Word and use Save As → PDF → Options → Encrypt with a password, or install LibreOffice and use File → Export as PDF → Security. All three are free with software you likely already have; none requires an Acrobat subscription. ### Which free method gives the strongest encryption? LibreOffice, which offers AES-256 in recent versions. macOS Preview and Microsoft Word both produce AES-128. AES-128 is not broken and is fine for ordinary business documents, but if you specifically need 256-bit, LibreOffice is the free route to it. ### Can a PDF password be removed or cracked? A strong, random password on AES encryption is not realistically brute-forced. The practical weaknesses are elsewhere: short or guessable passwords fall to dictionary attacks in minutes, and a permissions password, the kind that only restricts printing or copying rather than opening, is stripped instantly by freely available tools, because the file itself is not encrypted at all. ### Is it safe to use an online PDF password tool? Consider what you are doing: uploading a confidential document, unencrypted, to a stranger's server so it can be encrypted there. The service also necessarily sees your password. For anything genuinely sensitive, use the offline methods on your own machine instead, they are free and take the same amount of time. ### How do I send the password to the recipient? Never in the same email as the file, that defeats the entire exercise, since anyone who intercepts or is forwarded the message gets both halves. Send the password through a different channel, such as a text message or a phone call. ## Related guides - [How to share files securely by link](https://linkinseconds.com/blog/share-files-securely-by-link), and what “secure” really means. - [Share a PDF people can view but not download](https://linkinseconds.com/blog/share-a-pdf-people-can-view-but-not-download) - [Send a file that self-destructs after it's opened](https://linkinseconds.com/blog/send-a-file-that-self-destructs) ## Keep reading - [Send a pitch deck, see who opens pitch.pdf Live lisview.com/pitch How to send a pitch deck and see exactly when investors open it 5 min read](https://linkinseconds.com/blog/send-a-pitch-deck-and-see-who-opened-it) - [Deliver a lead magnet, get the email free-guide.pdf Live lisview.com/guide How to deliver a lead magnet PDF and capture emails (2 ways) 7 min read](https://linkinseconds.com/blog/deliver-a-lead-magnet-pdf-and-capture-emails) - [See who read page 4 free view tracking deck.pdf Live lisview.com/deck The free DocSend alternative: see who opens your documents (2026) 6 min read](https://linkinseconds.com/blog/free-docsend-alternative) ## Turn any file into a link in seconds Upload a PDF, image, video, or ZIP and get a clean, trackable link with a QR code, free. [Try Link in Seconds →](https://linkinseconds.com/) Source: https://linkinseconds.com/blog/password-protect-a-pdf