Add a password to any PDF, encrypt PDF with AES-256, and lock PDF from editing or copying — no Adobe Acrobat, no Foxit, no signup needed.
Drop your PDF to add password protection
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TL;DR — Password Protect a PDF in 30 seconds
Three steps. Under 30 seconds. Files never leave your browser.
Click Browse or drag and drop your PDF. Works on desktop, iPhone, and Android.
Enter an open password that recipients will need to view the PDF. Optionally set an owner password and restrict printing, copying, or editing.
Click Protect PDF and download your encrypted file instantly — fully compatible with Adobe Acrobat, Preview, and all major PDF viewers.
Whether you need to add a password to a PDF on Windows 10, Mac, iPhone, or Android, PDFcrest handles it in seconds — no software installation needed. You can encrypt a PDF file with AES-128 or AES-256, set a password for a PDF before emailing it, or create an encrypted PDF from any existing document. Common searches in this area include how to add password protection to a PDF online free, put a password on a PDF, and make a PDF password protected without Adobe Acrobat, Foxit, Soda PDF, or Bluebeam.
PDFcrest lets you protect a PDF from copying and lock a PDF from editing using owner password permissions — the same mechanism used by Adobe Acrobat and Foxit. This is useful when you need a non-copyable PDF for published reports or course materials, want to apply PDF anti-copy protection, restrict printing, or block annotations. You can also protect a PDF from sharing or redistribution by combining an open password with permission restrictions.
PDFcrest works as a browser-based tool across all platforms. If you're looking to password protect a PDF on Mac, encrypt a PDF on Windows 10 or 11, lock a PDF on iPhone, or secure a document on Android, the process is identical — upload, set your password, and download. No desktop PDF locker software or paid subscription like Adobe Acrobat Pro is required on any platform.
If you need to work with an existing secured document, common tasks include opening a password-protected PDF, converting a protected PDF to Word, printing a locked PDF, or removing security from a PDF you own. These tasks require the original owner password. PDFcrest focuses on adding protection — to remove a password from a PDF you already own the credentials for, you can use our Unlock PDF tool.
Many businesses receive or send password-protected PDF statements — bank statements, payroll slips, and tax documents are commonly delivered this way. PDFcrest makes it easy to apply the same protection to your own financial documents before sharing them with clients, accountants, or HR teams. The tool supports the document open password and owner permissions password model that Adobe, banks, and enterprise PDF workflows rely on.
For teams that need to password protect multiple PDF files at once or integrate PDF encryption into an automated workflow, the PDFcrest REST API supports batch processing — including the ability to apply different passwords to different files programmatically. This is useful for document management systems, HR platforms, and any workflow that generates protected PDFs at scale.
Why PDFcrest
256-bit AES encryption, permission controls, no daily limits, no signup — professional PDF security for free.
Protect PDF with password using the highest PDF encryption standard — 256-bit AES, the same level used by Adobe Acrobat Pro. Industry-grade security for free.
Set printing, copying, and editing restrictions independently. Restrict PDF permissions with an owner password to prevent unauthorised changes while allowing viewing.
Password protect PDF free with no daily limit, no account, and no subscription. Protect as many documents as you need without any paywall.
Password protect PDF on iPhone, iPad, Android, or desktop in your browser. No app needed.
Protected PDFs work with Adobe Acrobat, Apple Preview, Chrome, Firefox, and all major PDF viewers and mobile apps.
Encryption runs locally via WebAssembly (MuPDF). Your PDF and password are never transmitted anywhere — there's no upload to intercept and nothing stored on a server.
Comparison
| Feature | PDFcrest | Adobe Acrobat Online | SmallPDF / ilovePDF |
|---|---|---|---|
| Password Protect PDF — Free | ✓ Always free | ✗ Acrobat Pro required | ✗ 2 tasks/day |
| No Signup Required | ✓ Zero signup | ✗ Adobe account | ✗ Email required |
| No Watermarks | ✓ Never | ✓ | ✗ Free adds watermark |
| 256-bit AES Encryption | ✓ Full AES-256 | ✓ | ~ AES-128 on free |
| Permission Controls | ✓ Full controls | ✓ | ~ Limited on free |
| File Deleted After Download | ✓ Immediately | ~ Varies | ~ 1 hour |
| AES-128 + AES-256 Choice | ✓ Choose either | ~ Pro required | ~ AES-128 only |
Use Cases
From individuals to enterprise teams — everyone needs to secure PDF documents.
Password protect confidential PDFs — contracts, NDAs, financial reports — before emailing to clients or partners. Only recipients with the password can open the file.
Restrict printing and copying on legal documents to prevent unauthorised distribution. Use owner passwords to control who can modify a PDF after it leaves your organisation.
Add open passwords to premium course materials, e-books, or exam papers. Share with registered students only — prevent wider unauthorised distribution.
Protect a PDF containing pricing or sensitive strategy information before sharing with prospects. Set print-restriction to prevent proposals being passed beyond the intended recipient.
Encrypt sensitive PDF reports before distribution within government systems. 256-bit AES encryption meets data protection requirements for public sector document security.
Protect PDF on iPhone in Safari before sharing via email, AirDrop, or iMessage. Ensure your document is encrypted before it leaves your device.
Encrypt PDF files containing salary slips, invoices, and financial reports before sending — mirroring how banks deliver password-protected statements by default, with a password only the intended recipient can open.
Protect PDF files containing patient reports, prescriptions, and medical records so sensitive data stays private in transit — a free alternative to costly PDF encryption software in healthcare workflows.
Freelancers and agencies can password protect PDF proofs, proposals, and creative briefs before sending — preventing unauthorised distribution of work-in-progress files.
Workflow Recipes
Protecting a PDF is usually one step in a larger workflow. Here are the tool combinations PDFcrest users chain together most often.
Convert a Word document to PDF first, then add a password before sending it to a client or external recipient.
Shrink the file size first — encrypted content compresses poorly — then encrypt the smaller result so it's ready to email.
Combine several related documents into one file, then add a single password to secure the whole bundle at once.
To change a password or edit an already-encrypted PDF, remove the existing password first, make your changes, then protect it again.
Splitting a large document into separate files for different recipients? Add a distinct password to each part after splitting.
Technical Detail
When you password protect a PDF, PDFcrest applies 256-bit AES encryption to the document — the highest encryption level defined in the PDF 1.7 and PDF 2.0 standards, and the same algorithm used by Adobe Acrobat Pro. The encryption wraps every content stream, font, image, and resource in the PDF so that the file cannot be read without the correct password.
PDFcrest supports two types of PDF passwords: the open password (also called the user password) which recipients must enter to view the document, and the owner password which controls permissions such as printing, content copying, and document modification. These can be set independently — for example, you can allow viewing but restrict printing.
The resulting protected PDF is compatible with all major PDF viewers including Adobe Acrobat, Apple Preview, Google Chrome, Firefox, and mobile PDF apps. You can further compress the protected PDF or merge it with other PDFs using PDFcrest's free tool suite.
Under the Hood
No black box — this is the literal permission flag math MuPDF runs when you check "No Print," "No Copy," etc.
PDF permission bitmask (starts fully open):
perms = -4 # 0xFFFFFFFC — every permission allowed by default
if (noPrint) perms &= ~4 # clear bit 2 — printing
if (noEdit) perms &= ~8 # clear bit 3 — modifying content
if (noCopy) perms &= ~16 # clear bit 4 — copying / extracting text
if (noAnnotations) perms &= ~32 # clear bit 5 — adding comments/annotations
doc.saveToBuffer({
encrypt: keyLength === '256' ? 'aes-256' : 'aes-128',
'user-password': openPassword,
'owner-password': ownerPassword || openPassword,
permissions: perms
})
| Checkbox | What it actually clears |
|---|---|
No Print | Clears the printing permission bit — viewers can open the file but the reader should block/grey out printing. |
No Copy | Clears the content-extraction bit — text and image copy/selection is blocked by compliant readers. |
No Edit | Clears the modify bit — the document can be viewed but not altered in a compliant editor. |
No Annotate | Clears the annotation bit — comments, highlights, and form-filling are blocked. |
owner-password fallback | If you leave the owner password blank, it defaults to your open password — so permissions are still enforced even if you only set one password. |
FAQ
Answers to the most common questions about encrypting and securing PDF files
References & Further Reading
Page last updated: · Written and maintained by the PDFcrest team. The permission bitmask shown above is taken directly from the code running on this page.