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About this tool
Why this tool never encrypted PDFs — and the browser and desktop tools that genuinely do.
PDF Set Password does not add a password to a PDF, and this page is honest about that. Protecting a PDF is not a flag written into the file: the password must be turned into an encryption key, and then every string, image and stream inside the document has to be re-encrypted with it and the scheme recorded in the file's /Encrypt dictionary. The libraries behind this tool can detect that encryption and undo it when you already know the password, but they cannot apply it. An earlier version of this page returned your upload unchanged and told you the password had been applied — those downloads were never encrypted, so if you shared one, treat it as sent in the clear. Instead of a button that lies, this page points you to Protect PDF in our AltFLovePDF suite — which performs real AES-256 encryption in your browser tab, without uploading the document — and to the desktop software that does the same offline.
Open PDF Set Password on AltFTool — it loads instantly in your browser.
Open Protect PDF in the AltFLovePDF suite on this site, or pick an offline method: Preview on macOS, Microsoft Word, LibreOffice or Acrobat Pro.
Set a strong password and encrypt the PDF — the browser tool derives an AES-256 key and re-encrypts the document in your tab, without uploading it.
Reopen the encrypted file to confirm it demands the password before you send it, and share the password through a different channel than the file.
There is no upload box and no download on this page, because handing you an unchanged file labelled protected is the one outcome that could get a sensitive document leaked.
Encryption has to rewrite every string and stream in the document under a key derived from the password. The libraries behind this tool can undo that when you know the password; applying it takes a full security-handler implementation.
Protect PDF in our AltFLovePDF suite re-encrypts the document with AES-256 in your tab, and Preview, Word, LibreOffice and Acrobat Pro all do it offline — none of them upload the file.
Adding AES-256 protection, removing a known password, permanent redaction, metadata cleanup and watermarking all genuinely happen in your browser, and each is linked from the page.
No. Adding standard PDF protection means deriving an encryption key from your password and re-encrypting every string and stream in the document, and this tool never did that — an earlier version only pretended to. On this site, Protect PDF in the AltFLovePDF suite genuinely does it, with AES-256, in your browser tab.
No. That earlier version read your upload and handed the same bytes straight back with a new filename and a success message. Those files carry no protection at all and open for anyone. If you emailed or shared one believing it was locked, treat the contents as disclosed.
On this site, open Protect PDF in the AltFLovePDF suite: it encrypts with AES-256 in your tab and never uploads the file. Offline, Preview on macOS (File then Export, tick Encrypt), Microsoft Word (Save As PDF, then Options, then encrypt with a password), LibreOffice (File then Export As, Security tab) and Acrobat Pro all work too.
Because the failure mode is invisible: an earlier version of this very page handed back unencrypted bytes with a success message. In-browser encryption is possible — our Protect PDF does it — but verify any result yourself: reopen it in a fresh browser tab or a PDF reader. A genuinely encrypted file refuses to display until you type the password.
It can add protection and remove it. Protect PDF in the AltFLovePDF suite encrypts with AES-256, while PDF Delete Password and Unlock PDF perform real decryption in the tab, deriving the key from the password you supply and writing out a copy without the encryption dictionary. None of them can guess or crack an unknown password.