Password-Protect a PDF (and Remove It Later)

Sending something sensitive - a contract, a bank statement, an ID scan? A password on the file is a simple, genuinely effective layer of protection, and it takes about fifteen seconds to add.

Locking a PDF

Protect PDF encrypts your file with AES-256, the same standard used for documents that actually matter. Anyone who wants to open it will need the password you set. Set it, download the protected copy, share it.

The part people get wrong is not the encryption, it is the delivery. Send the password through a different channel than the file. Emailing a locked PDF and then emailing the password in the next message protects you against essentially nothing - anyone who can read one message can read the other. Text the password, say it on a call, use a different app. The whole value of the exercise is that the file and the key do not travel together.

Also worth doing: pick a password that is not the recipient's date of birth or the invoice number. Encryption is only as strong as the thing guarding it, and a four-digit code on an AES-256 file is a four-digit code.

One honest warning: there is no recovery. Encryption works precisely because the file genuinely cannot be opened without the password. We cannot reset it, and neither can anyone else. If you forget it, the document is gone. Store it in a password manager before you close the tab.

Removing a password

Unlock PDF produces a copy with no password prompt. That is useful more often than it sounds - you are tired of typing it every time you open a statement, or you need to merge the file with others and the page tools cannot read an encrypted document.

We are deliberately upfront about what this is: it removes protection from a PDF you can already open, by supplying the current password. It is not a password cracker. It cannot open a file you do not have the password for, and it is not going to become able to.

Any site claiming otherwise is either lying to you or doing something you do not want near your documents - and quite often both. A tool that genuinely could break AES-256 would not be a free web page with banner ads.

There is a second kind of PDF restriction worth knowing about: permissions passwords, which claim to prevent printing or copying while still letting anyone open the file. Those are a much weaker mechanism - the document is not really encrypted against you, the viewer is just asked politely to enforce a rule. Do not rely on them for anything you would rely on a real password for.

When a watermark is the better call

Sometimes you do not need to lock people out. You need to mark a document's status so nobody mistakes a draft for the final version.

Watermark PDF stamps text like DRAFT or CONFIDENTIAL diagonally across every page, semi-transparent so the content underneath stays readable. It travels with the file: printed, screenshotted, forwarded three times, the mark is still there. A password cannot do that, because once someone opens the file the protection has done its job and stepped aside.

The two solve different problems, and it is worth being clear which you have:

• Encrypt when the content is private and you are controlling who can open it.
• Watermark when the content is going to circulate and you are controlling how it is understood - not final, not for distribution, not the signed copy.
• Both, occasionally: a confidential draft going to a named reviewer.

A watermark is not security. Anyone determined can remove it. It is a labelling tool, and it is very good at that.

The finishing touches

Add Page Numbers is the small thing that makes a combined or printed document usable - "see page 14" only works if there are page numbers. It matters most on documents assembled from several sources, where the original numbering restarts partway through.

A sensible order of operations, if you are doing all of it:

1. Merge or Organize the pages into final shape
2. Add Page Numbers
3. Watermark if it is a draft
4. Compress if it needs to fit a limit
5. Protect last

Protect last, because an encrypted PDF is opaque to the other tools - they cannot read the pages to work on them. Doing it first just means unlocking it again.

Limits

PDFs are capped at 50 pages and 20 MB. Everything you upload and everything you download is deleted from our servers an hour later, encrypted files included - and we never see or store the passwords you set.

Encrypt when it is private, watermark when it is just not final.