Free online PDF password protection. Apply AES encryption (your choice of AES-128 for maximum compatibility or AES-256 for maximum security), restrict editing, copying and printing, and download the protected PDF in seconds. No account. No watermark. No installation.
Last updated: May 2026
Password protect any PDF document in seconds. Upload your file, add a password to encrypt the PDF (or set a permissions password to restrict editing, copying and printing), and download the encrypted file — all directly in your browser. OneClickPDF Protect PDF applies AES encryption (FIPS 197 compliant — both AES-128 and AES-256 are supported), and works as a free Adobe alternative for password-protecting PDFs. There is no registration, no ads while working on the encrypted PDF, and no software to install. Works on Windows, macOS, Linux, iOS and Android.
Drop your PDF here
or click to browse
The full upload-encrypt-download workflow takes most users under 30 seconds. The tool does not require account creation or email verification — drop your file in, and your PDF is encrypted within 5 seconds of choosing your password.
Drag your PDF onto the upload area or click 'Click to Browse' to browse from your device. Files up to 50 MB are supported. The file is loaded into your browser memory — it is never transferred to a server.
Pick which kind of protection you need. An open password (also called the user password or document open password) requires anyone to enter the password before they can view the file. A permissions password (also called the owner password) lets anyone view the file but restricts editing, copying, and printing. Apply both to encrypt the PDF and constrain what authorized viewers can do.
Type your password — at least 12 characters mixing uppercase, lowercase, numbers and symbols — to add password protection to the PDF. The real-time strength meter shows weak, medium, or strong while you type. The password is used in your browser to derive the encryption key — it is never logged, stored, or transmitted to any third party.
Click 'Protect & Download'. The protected PDF is encrypted with AES (your choice of AES-128 for maximum compatibility or AES-256 for maximum security) and downloaded directly to your device — your password is never stored anywhere.
PDF supports two distinct password types defined in ISO 32000-1 and ISO 32000-2. Most users only need the open password, but understanding both lets you apply the exact restriction your document requires.
An open password forces every recipient to enter the correct password before the PDF will display its content. Without the password, the PDF reader shows only an authentication dialog. Use this when you want to password protect a PDF document for confidential contracts, financial statements, medical records, or any file where a viewer should not see content unless explicitly authorized.
A permissions password (or owner password) lets anyone open and view the PDF but restricts what they can do with it. You choose which actions are blocked: editing, content copying, page extraction, comments, form filling, and printing (with a separate print-quality option). Set this when you want to protect a PDF from editing without forcing recipients to enter a password to read it.
Apply both password types on the same PDF for layered protection: an open password gates initial viewing, and a permissions password constrains what authorized viewers can do once they are inside. This is the standard configuration to protect a PDF from copying, editing, and printing on legal documents, M&A diligence material, court filings, and pharmaceutical regulatory submissions.
OneClickPDF supports both AES-128 (default — maximum compatibility with older Adobe Reader versions) and AES-256 (maximum security, FIPS 197 + ISO 32000-2 compliant). Most competitors fix you to a single algorithm; OneClickPDF lets you decide based on your recipient’s PDF reader. The cryptographic margin matters for documents that may need to remain secure for 10+ years against future improvements in computing power.
Adobe Acrobat Online charges USD 23.99/month to password protect PDF documents alongside other features. Smallpdf limits free users to 2 tasks per day on a 5 MB cap. OneClickPDF Protect PDF is genuinely free with no daily, hourly or page limits, and the encrypted PDF carries no watermark of OneClickPDF whatsoever.
Encryption runs in your browser via QPDF compiled to WebAssembly. Your file is loaded into browser memory, encrypted with your password, and the result is downloaded — at no point is your PDF sent to a server. There is nothing for OneClickPDF to log, retain, or delete because there is no server-side copy at any stage.
Browser-only architecture means the tool works on any device with a modern browser. There is no Windows installer, no macOS .dmg, no mobile app to download. Encrypt PDFs from your iPhone before emailing them or lock a sensitive document on a Chromebook in the school library.
Skip the registration wall that defines competitors like Adobe Acrobat Online. Encrypt your first PDF within 5 seconds of arrival on the page — no email verification, no payment information, no upgrade prompts.
As you type the password, a meter shows weak, medium, or strong so you commit to a strong password before encrypting. Combined with the published PDF password best practices (12+ characters, mixed case, numbers, symbols), this dramatically reduces the risk of brute-force attack on the encrypted file.
Capability-by-capability, OneClickPDF is the only fully-free option that runs entirely in the browser, supports both AES-128 and AES-256, and requires no account.
| Feature | SmallPDF | iLovePDF | Sejda | PDF24 | Adobe | Ours |
|---|---|---|---|---|---|---|
| Free, unlimited PDFs | ✗ 2/day | ✗ Daily | ✗ 3/hr | ✓ | ✗ Paid | ✓ |
| No account required | Trial sign-up | ✗ | ✓ | ✓ | ✗ | ✓ |
| Files stay in browser | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ |
| AES-128 supported | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| AES-256 supported | ✗ Free | ✓ | ✓ | ✓ | ✓ Pro | ✓ |
| Open + permissions password | Open only (free) | Both | Both | Both | Both | ✓ |
| Real-time strength meter | ✓ | ✗ | ✗ | ✗ | ✓ | ✓ |
| No watermark on output | ✗ + Protect | ✓ | ✓ | ✓ | ✓ | ✓ |
| Mobile encryption | App needed | App needed | Browser | Browser | Browser + app | ✓ |
| Pricing | USD 9+/mo | USD 9/mo Premium | Free | Free | USD 23.99+/mo | ✓ |
Competitor information was accurate at time of publication and may have changed.
Bottom line: OneClickPDF is the only fully-free option that runs encryption entirely in your browser (your file never leaves your device), supports both password types in the free tier, and requires no account. Adobe Acrobat is the only viable alternative when you also need certificate-based encryption or US federal compliance documentation, but you pay USD 23.99/month for it.
Tax returns, salary slips, audit reports, and bank statements contain personally identifiable financial information. Encrypt them before emailing your accountant, lender, or tax authority. AES protection meets the data-sharing standards of US FFIEC, UK FCA, and EU PSD2.
Medical records, lab reports, and prescription PDFs containing Protected Health Information (PHI) must be encrypted at rest under HIPAA's Security Rule (45 CFR § 164.312). Apply a strong open password before sending PHI to a colleague, patient, or insurer.
NDAs, M&A diligence material, court filings, and discovery production sets carry attorney-client and work-product privileges. Apply both an open password (controls who can view) and a permissions password (blocks copy / print / extract) to maintain privilege when sharing across opposing counsel.
Offer letters, payroll reports, and performance reviews include personal data covered by GDPR (EU), CCPA (California), and PIPEDA (Canada). HR teams should encrypt PDFs before storing them in shared drives or sending to managers.
Management decks, financial forecasts, and board books should be restricted from accidental forwarding. Apply a permissions password to prevent printing, copying, and extracting — recipients can read on screen but not redistribute the underlying data.
Drop your file, set a password, choose AES-128 or AES-256, download — under 30 seconds, no account, no upload.
Start protecting nowSign PDF Online Free
Draw your signature, type it, or upload an image — then place it anywhere on your PDF in seconds. Legally valid under the ESIGN Act (US), eIDAS (EU), and Electronic Communications Act (UK). No account is needed.
Unlock PDF
Remove password protection from a PDF you own.
Redact PDF
Permanently black out names, account numbers, addresses, or any sensitive content before sharing. Redactions are baked into the file — not just overlaid.
Watermark PDF
Add text or image watermarks to protect your documents.