Add a real password to a PDF so only people who know it can open the file — built entirely in your browser, with no upload step. Set the password, choose what's allowed once it's open, and download a protected copy.
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Encryption happens entirely in your browser's memory. Neither the file nor your password is ever sent anywhere.
Browsers don't have a built-in way to reach into an arbitrary PDF's internal structure and lock it with a password — that kind of low-level file encryption normally needs a dedicated desktop program or a server doing the work. This tool gets the same practical result, a file that genuinely requires a password to open, by rebuilding your PDF from scratch around secured page images and applying a real, standard PDF password scheme to the new file as it's created.
The visual result looks identical to the original — same pages, same layout — and the password gate it ends up with is read correctly by ordinary PDF readers, including Adobe Acrobat, Adobe Reader, and the PDF viewers built into Chrome, Firefox, and Edge.
FIG. 1 — Upload → Set password → Choose quality → Download
"Encrypt a PDF" can mean different things depending on what you're trying to prevent. This flowchart points to whether this tool, or a different approach, fits what you actually need.
FIG. 2 — Matching what you need to protect with the right tool
Every page of your PDF is first rendered to a secured image at the quality you choose, the same rendering technology used throughout this site's other tools. Those images are then placed, one per page at the original page size, into a brand-new PDF as it's being built. As that new file is generated, a standard PDF password scheme — the same Standard Security Handler that's been part of the PDF specification for decades — is applied directly to it, using the password and permissions you set.
That handler is what makes Adobe Reader, browser PDF viewers, and virtually every other PDF program prompt for a password before showing the page: it's not a custom lock unique to this tool, it's the same mechanism professional PDF software has supported for years, which is why the result opens correctly outside this site.
Password-protecting a document is usually a sign it's sensitive — exactly the kind of file, and the kind of password, you don't want passing through someone else's server on the way to being secured. Plenty of free online encryption tools do exactly that: upload the file, process it remotely, and send back a result, with your chosen password traveling there too.
This tool keeps the entire process local. The PDF you choose is read into your browser's own memory, the password fields are read directly by your browser's own JavaScript, and the final encrypted file is assembled there too, using your device's own processing power. Neither the file nor the password is transmitted anywhere else at any point. Closing the tab clears everything from memory, with nothing cached, logged, or stored by this tool afterward.
Password fields, the show/hide toggle, the quality selector, and the print and copy checkboxes are all sized comfortably for a thumb, with the show-password toggle especially useful on a phone keyboard where typing a password blind is more error-prone than on a full keyboard. The page preview strip lets you confirm you've loaded the right file before typing in a password at all.
The encrypted file downloads the same way any file does on your phone's browser, ready to attach to a message or email from there.
Because this tool works entirely in the browser without a server doing the heavy lifting, the password protection it applies comes from rebuilding the file around page images rather than encrypting the original PDF's existing structure directly. The practical cost is real: text in the protected file can no longer be selected, copied, or searched, and the file is somewhat larger than the unprotected original, especially at the higher quality setting.
What you get in return is a password gate that's genuinely enforced by the PDF format itself — not a polite request, but a real barrier that standard PDF software actually checks before rendering the page — built without uploading anything to a third party. For most documents people want to password-protect, like a finished answer key or a personal scan, losing text selectability is a small price for not having to install desktop software or trust a server with the file.
| Approach | Cost | Privacy | Result |
|---|---|---|---|
| This browser-based tool | Free | File and password never leave your device | Genuine password gate; text becomes a secured image |
| Adobe Acrobat's password protection | Often paid or limited trial | Local, but requires installation | Keeps text selectable while encrypting the original structure |
| Putting the PDF in a password-protected ZIP file | Free, built into most operating systems | Fully local | Protects the file in transit, but the PDF itself opens freely once extracted |
| Server-based online encryption tools | Often free with limits | File and password are uploaded to a remote server | May keep text selectable, at a real privacy cost |
| Not protecting the file, just being careful who you send it to | Free | Fully local | Relies entirely on trust, with no protection if it's forwarded |
If keeping the text selectable and searchable matters as much as the password itself, desktop software that encrypts the PDF's original structure directly is the better fit, since it doesn't need to flatten pages to images first. If the priority is a quick, no-install, no-upload way to make sure a file can't just be opened by anyone it's forwarded to, this tool covers that directly, and a password-protected ZIP is worth considering as a complementary layer for the file in transit.
This tool relies on standard browser features — reading a local file, rendering pages to canvas, and assembling a new file in memory — that work in current versions of Chrome, Firefox, Edge, and Safari, on both desktop and mobile, with nothing to install beforehand.
Because everything runs on your own device, the practical limit on how large a file you can comfortably encrypt depends on your device's available memory and processing power rather than any cap built into the tool. Typical exam papers and answer scripts, running from a handful of pages up to a few dozen, process in a few seconds at Standard quality on most laptops and recent phones. Long documents at High quality take noticeably longer and produce a larger file, since every page is being rendered at a higher resolution before being packed into the new PDF.
The password fields, permission checkboxes, and quality selector are all standard, labeled form controls that work correctly with keyboard navigation and screen readers. The output file itself, however, is not: because protecting it converts every page into an image, a password-protected PDF from this tool can't be read aloud by a screen reader or have its text resized as text, the same accessibility limitation any fully image-based PDF has.
If a document needs to stay accessible to screen reader users and also needs a password, that combination isn't something a fully browser-based, server-free tool can offer today — it's worth keeping an unprotected, accessible original on hand for anyone who needs it, and using this tool's output only where a password is the higher priority.
Yes. There is no sign-up and no charge for encrypting any number of PDF files, with no limit on how many times you use it.
No. The entire process runs inside your web browser, so there is nothing to download or install on Windows, macOS, Chromebooks, or Linux.
No. Both the file and the password you set are handled entirely inside your browser's memory and are never sent to any server, so neither your document nor your password is ever transmitted anywhere.
No. To apply genuine password protection entirely in the browser, this tool converts each page into a secured image before rebuilding the file, so the resulting PDF looks identical but its text can no longer be selected, copied, or searched.
The file becomes permanently unopenable. This tool never stores or transmits your password, so there is no recovery option here or anywhere else; keep your password somewhere safe before you close the tab.
Yes. This tool applies the standard PDF security handler that virtually every PDF reader, including Adobe Acrobat, Adobe Reader, and built-in browser PDF viewers, already knows how to prompt a password for.
Yes. Separate checkboxes let you allow or block printing and copying independently of the password needed to open the file.
Yes. The password fields, permission toggles, and quality selector are all sized for touch and have been built to work smoothly in mobile browsers such as Chrome on Android and Safari on iPhone.
Protecting a file often comes at the end of a longer workflow. These tools cover the rest, from organizing and labeling to comparing versions, filling forms, and archiving — each one running the same client-side way, with no file uploads.