Require a password to open the file
Open password is the one required field. The protected copy asks for that password every time someone opens it, and the content stays encrypted until they type it correctly.
Protect PDF with a password
or drop a file anywhere here
Files other than PDF are converted first. Signing in raises the size limit.
Or start from a blank IRS form
Browse all IRS forms →- You add
- One PDF
- You set
- An open password, plus an optional permissions password
- You get
- A copy encrypted with AES-256
Protecting a PDF means encrypting it so the file opens only for someone who types the right password. This tool adds an open password to your PDF and encrypts the copy with AES-256. You can add a second, optional permissions password that tells PDF readers to block printing and editing. Drop one PDF in the box above, type the password, select Run Protect PDF and download the protected copy. Pages, bookmarks and form fields stay as they were. One file needs no account, the upload travels over HTTPS, and indox deletes free-tier files automatically within 24 hours after the job finishes.
What can you do when you protect a PDF?
Encrypt with AES-256
indox writes every protected copy with AES-256 encryption. You do not pick an algorithm or a strength level, and the tool has no weaker fallback.
Block printing and editing
Fill in Permissions password and indox flags the copy so PDF readers that honor the setting refuse to print or change it. Copying text and filling in form fields stay allowed.
Keep bookmarks, forms and attachments
Protection changes who can open the file and what readers let them do with it. Bookmarks, form fields and attached files travel into the protected copy.
What protecting keeps and what it changes
Stays the same
- Page content and page order.
- Bookmarks, form fields and attachments. The file is copied whole and then encrypted.
- The file on your device. You download a new, encrypted copy.
Changes
- The copy is encrypted with AES-256 and opens only with the Open password.
- If you leave the Permissions password empty, the owner password is set equal to the open password. Anyone who can open the file then has every right on it.
- If you type a Permissions password, the copy sets printing and editing to off. Copying text and filling forms stay on.
Which passwords to fill in
| You want | Fill in | What the copy does |
|---|---|---|
| A file that only people with a password can open | Open password only | Without the password the file does not open. With it, every permission is allowed. |
| The same, with printing and editing switched off | Open password and a different Permissions password | The copy asks for a password to open and sets printing and editing to off. Copying text and filling forms stay on. |
How to protect a PDF in 3 steps
Drop your PDF
Drop one PDF on the box at the top of this page, or click the box to browse. The file name and size appear next to a Replace button.
Type the passwords
Fill in Open password. Add a Permissions password only if you want to block printing and editing, then select Run Protect PDF.
Download and test the copy
Select Download when the job finishes. Open the copy and type the password once to confirm it works before you delete the unprotected original.
Why protect a PDF with indox?
The form has two fields, and each one maps to a real change in the file. Open password locks reading behind AES-256 encryption. Permissions password switches off printing and editing. Nothing else about the document changes: the pages, bookmarks, form fields and attachments arrive in the copy as you uploaded them. If indox cannot protect the file, the job ends with an error message, so you never download an unprotected PDF by mistake. One file runs without an account, and both the upload and the download use HTTPS.
- AES-256 encryption on every protected copy
- Open password required, permissions password optional
- Bookmarks, form fields and attachments kept
- A failed job shows an error and produces no file
- No sign-in for one file
What are the limits when you protect a PDF?
- Size
- The free tier has a file size limit. Signing in raises it, and paid plans raise it further.
- Formats
- This tool works on PDF files. To change a file's type, use the PDF converter.
- Privacy
- Files are encrypted in transit and processed on indox infrastructure.
- Deletion
- Free-tier files are deleted automatically within 24 hours after the job finishes. Signed-in output stays in your history for your plan's retention period.
Limits worth knowing
- indox cannot recover a forgotten open password or reopen the file for you. Store the password safely, and keep your original until you have tested the copy.
- The permissions password relies on PDF readers to enforce it. Readers that honor the flags block printing and editing, software that ignores them does not, and anyone who knows the open password can save an unrestricted copy.
- A PDF that already needs a password to open cannot be protected again here, because the form has no field for the current password. Unlock it first, then protect the unlocked copy.
- The form removes spaces at the start and end of each password, and it has no confirm field. Type carefully and test the copy.
- Protect a file as the last step. Compress it, watermark it or add page numbers first, then protect the final copy.
When the protected copy is not what you expected
| What you see | Why | What to do |
|---|---|---|
| A reader asks for a password I did not mean to set | The Open password is required in this form, so every protected copy needs one | To restrict printing or editing on a file that anyone can open, use Change Permissions. |
| Printing or editing still works in some programs | Permission flags are enforced by the software that opens the file, and the PDF format cannot force a program to honor them | Rely on the Open password for real protection. |
| The tool cannot protect a file that already needs a password | The form has no field for the current password | Remove it with Unlock PDF, then protect the open copy. |
| A later step on the protected copy asks for a password or fails | The copy needs its open password before any program can read its pages | Protect the file as the last step, after you compress, watermark or number it. |
What do the free and paid plans add?
Free
- All converters
- Daily credit refresh
- Email support
Basic
- Access to all features
- AI Extract
- Priority conversions
- Email support
Highest priority
Premium
- Everything in Basic
- Highest priority queue
- Larger file limits
- Priority support
Pay-As-You-Go
- No subscription
- Credits never expire
- Opt-in auto-refill
- Access to all features
What else can you do with a PDF?
Who protects PDFs?
Freelancers and bookkeepers
You email invoices, tax forms and statements that carry account numbers. An open password keeps the attachment unreadable if the message lands in the wrong inbox.
HR and operations staff
You send offer letters, contracts and payroll summaries to one person at a time. Protect each file and share its password through a different channel, such as a phone call.
Authors and consultants sharing drafts
You want a client to read a report on screen while printing and editing stay off. Set both passwords, knowing the restriction depends on the reader app.
When to protect a PDF
- Before you email a bank statement, tax return or ID scan.
- When a contract goes to a client and only the signer should open it.
- When you store a PDF in a shared drive that other people can browse.
- When reviewers should read a draft on screen with printing switched off.
- After you finish compressing or watermarking a file and it is ready to send.
Where can I read more?
Sources
- Encryption and decryption of PDFspypdf documentation
- PdfWriter.encryptpypdf documentation
- Encryption, restrictions are enforced by softwareqpdf manual
Facts checked on October 16, 2026
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Protect PDF FAQs
What encryption does Protect PDF use?
AES-256. indox applies it to every protected copy, and no setting lowers it.
What is the difference between the open password and the permissions password?
The open password is required to read the file. The permissions password is optional, and when you set one indox flags the copy to block printing and editing.
Can I restrict printing without an open password?
This tool always sets an open password, because that field is required. Change Permissions, another indox tool, sets printing, editing, copying and form filling rules without one.
What happens if I forget the password?
indox cannot recover it. Unlock PDF also needs the correct password, so keep your original file or save the password in a password manager.
Can I protect a PDF that already has a password?
Unlock it first with its current password, then run the unlocked copy through this tool with the new one. indox cannot read a locked PDF without its password.
Does indox check how strong my password is?
No check runs on password strength. The form accepts any password that is not blank, so choose a long one that you do not use anywhere else.
Can I protect a PDF that is already signed?
Protecting writes a new, encrypted copy of the file. indox does not promise the signature survives in that copy, so check it in your PDF reader and keep the original signed file.
Do I need an account to protect a PDF?
One file runs without signing in. An account or a paid plan raises the limits.