PDFs can be locked in two ways: an "open password" that blocks the file from being opened at all, and a "permissions restriction" that blocks editing, printing, or copying. PDFnite's lock tool sets both at once with a single password — for free, in your browser. This guide walks through how to apply the lock, when to choose which type, and how PDFnite compares to other options.
Two Ways to Lock a PDF — Access Control vs. Permissions Restriction
PDFs support two distinct password mechanisms, designed for different goals.
| Type | Also called | What it blocks | Best for |
|---|---|---|---|
| Open Password | User password / access restriction | Opening the file itself. Without the password the contents stay inaccessible | Contracts, resumes — anything that shouldn't be readable outside its intended recipient |
| Permissions Restriction | Owner password / permissions password | The file opens normally, but editing, printing, and copying are blocked | Internal documents where you want to prevent edits, unauthorized printing, or copy-pasting |
"I want to lock the PDF from being edited" / "block printing" / "block copying" refers to a permissions restriction. "I want to restrict who can open it" refers to an open password.
How to Password Protect a PDF with PDFnite
PDFnite's lock tool performs encryption entirely in your browser. Files are never sent to a server, which makes it well-suited to confidential documents.
- Open the Lock PDF tool
- Drag and drop your PDF
- Enter the password twice (the second field is for confirmation)
- Click "Set Password"
- Download the password-protected PDF
PDFnite's Password Behavior (Important)
When you lock a PDF with PDFnite, the single password you enter is applied to both the open password and the permissions restriction at the same time. The resulting file behaves like this:
- The password is required to open the file (access restriction)
- Even after opening, editing, printing, and copying require the same password (permissions restriction)
PDFnite does not support fine-grained separation such as "allow opening but block printing only" or "different passwords for opening and editing." If you need that, use Adobe Acrobat or another paid professional service (see below).
Choosing the Right Approach
| Scenario | Recommended tool | Setup |
|---|---|---|
| Sending a contract or resume to someone specific (block outsiders) | PDFnite | Single password locks opening + permissions together |
| Preventing tampering or unauthorized printing of internal docs | PDFnite | Same — share the password with intended viewers |
| You need split permissions ("open freely but block printing only") | Adobe Acrobat / paid professional service | Configure user and owner passwords separately |
| Highly confidential — avoid uploads | PDFnite | Browser-only processing, no upload |
Comparison With Other Methods
Method 1: PDFnite (Browser-only, Free)
| Item | Details |
|---|---|
| Cost | Free |
| Install | None (browser only) |
| File upload | None (processed in-browser) |
| Permission granularity | ✕ Opens + permissions share a single password |
| Encryption | RC4 128-bit (adequate for standard business use) |
→ Simplest path to password protection, safe even for sensitive files.
Method 2: Adobe Acrobat
Acrobat's "Security Settings" provides detailed password protection. Open password and owner password can be configured independently, and the encryption level can be chosen.
- Pros: Granular permissions (e.g. block printing only), 256-bit AES encryption
- Cons: Paid subscription, installation required
Method 3: macOS Preview (Mac only)
On a Mac, "File → Export → Encrypt" in Preview applies a password.
- Pros: Built-in, no extra cost
- Cons: No granular permissions, not available on Windows
Frequently Asked Questions
How do I password protect a PDF?
Upload your PDF to PDFnite's lock tool, enter the password twice, and press "Set Password." That's the entire flow — three steps and the PDF is locked.
I want to block the PDF from being edited
Setting a password with PDFnite automatically enables the permissions restriction (owner password). After locking, the file can't be edited, printed, or copied without the same password.
Can I block printing only?
PDFnite can't apply a printing-only restriction — when a password is set, opening, editing, printing, and copying are all gated by the same password. If you need printing-only restriction, use Adobe Acrobat or another paid professional service.
Can I block copying only?
For the same reason, copy-only restriction isn't supported in PDFnite. Adobe Acrobat or a paid professional service is the right tool.
What if I forget the password?
A forgotten password generally means the file can't be opened by anyone. Store the password somewhere safe. If instead you need to remove a permissions restriction (owner password) on someone else's PDF, see PDFnite's unlock tool.
What encryption is used?
PDFnite uses RC4 128-bit encryption — sufficient for typical business use. If you specifically need AES-256, use Adobe Acrobat.
Can password-protected PDFs be opened in any viewer?
Yes. Locked PDFs can be opened in Adobe Acrobat Reader, browser-based viewers, macOS Preview, and other major readers once the correct password is entered.
Does it work on a smartphone?
Yes. PDFnite is browser-based, so the lock flow is the same on smartphones and tablets.
Summary
You can password-protect a PDF for free in your browser with PDFnite. Files are never uploaded, which makes it appropriate for contracts and personal data. If you specifically need granular permissions (block printing only, separate open and owner passwords), use Adobe Acrobat or another paid professional service.