The PDFs that most need a password, such as contracts, IDs, bank statements, medical records, and unpublished proposals, are exactly the ones you should least upload to an unknown server. Many online PDF encryption sites ask you to upload the file first, which means handing it to a third party in order to protect it. This article shows how to set a password, remove a password, and restrict permissions with ToolGarden's PDF Encrypt / Decrypt tool inside the browser, with the file staying on your computer. It also clarifies a few key ideas: the difference between the open password and the owner password, what permission restrictions can and cannot prevent, what determines encryption strength, and what to do if you forget a password.
First, what PDF encryption actually protects
Standard PDF encryption involves two kinds of password with entirely different jobs:
| Concept | Also called | Purpose | Without it |
|---|---|---|---|
| Open password | User password | Must be entered to open the document, otherwise the content cannot be read | You cannot view the pages; this is the lock that actually keeps strangers out |
| Owner password | Permissions password | Used to change the permission settings themselves | The file opens, but printing, copying, modifying follow the permission flags |
| Permission flags | Print / copy / modify / annotate | Declare which actions the file allows | Left to readers to honor; not unbreakable protection |
The last row is the most misunderstood. Permission restrictions are declarations stored in the file. Well-behaved readers obey them, for example by greying out Print, but not all software does, and some tools deliberately ignore them. So to stop strangers reading, rely on the open password. Use permission restrictions only as a nudge against casual copying or editing, never as a security measure.
Steps: set an open password
- Open PDF Encrypt / Decrypt and stay in Encrypt mode. Click the upload area to choose a PDF, or drop the file on it.
- Enter a password under Open password. It is required: the Encrypt & download button stays greyed out without it.
- Owner password is optional. If left empty, the tool makes the owner password the same as the open password; fill it in if you want a separate management password.
- Under Permissions, tick what is allowed: allow printing, allow copying text, allow modifying, allow annotations. The defaults allow printing and copying, and disallow modifying and annotating.
- Click Encrypt & download. The file is processed locally, a download link appears, and the file is named original-name-encrypted.pdf.
Steps: remove an existing password
If you received a password-protected PDF, you know the password, and you want a copy that no longer needs one (to merge, split, or archive it):
- Switch to Decrypt mode and upload the encrypted PDF.
- Enter the known password under Current password.
- Click Decrypt & download to get original-name-decrypted.pdf.
Two things to know. First, this is for removing a password you are entitled to use, meaning a file whose password you know. It is not a cracking tool and cannot recover a forgotten password. Second, when the password check fails, the tool tries to read the file another way and only reports "wrong password or the PDF cannot be decrypted" if both attempts fail. So if you typed a wrong password and still got an output file, open it and confirm the content is normal rather than assuming decryption worked.
What determines encryption strength
This is a fact most tutorials skip. PDF encryption has several generations, from ancient 40-bit RC4 through 128-bit RC4 and 128-bit AES, up to 256-bit AES. We read the source of the PDF encryption library the site uses (@cantoo/pdf-lib 2.7.1), and it picks the algorithm from the PDF version declared in the header of the file being encrypted:
| Header version of the source file | Algorithm used (per that library) | Assessment |
|---|---|---|
| PDF 1.4, 1.5 | 128-bit RC4 | Mediocre; RC4 is no longer recommended |
| PDF 1.6, 1.7 | 128-bit AES | Adequate for everyday confidentiality, widely compatible |
| 1.7 extension level 3 | 256-bit AES | Strongest, but a few old readers do not support it |
| Anything else (such as 1.3 and below) | 40-bit RC4 | Very weak; avoid for sensitive files |
In other words, the same click on Encrypt & download can end up with different algorithms for different source files, and the interface does not tell you which. Two practical tips. First, a file produced by tools such as Merge PDF or Organize PDF is a newly created document with a 1.7 header, so encrypting it afterwards lands in the 128-bit AES row. If you are handed a very old, low-version PDF, run it through Organize PDF once and export it unchanged, then encrypt that. Second, after encrypting, open the document properties in a reader and look at the Security or Encryption entry to confirm the algorithm actually used. It takes ten seconds and saves you from thinking a file is well protected when it is weakly protected.
Example: sending a quote and contract to a client
A 12-page contract and a 3-page quote go to a client. The goal: the client can open and print them but should not edit them casually, and the file cannot be read if someone intercepts the email.
1 Merge PDF: contract.pdf (12 pages) + quote.pdf (3 pages) -> merged.pdf (15 pages)
2 PDF Watermark: text CONFIDENTIAL, diagonal, opacity 0.2 -> merged-watermarked.pdf
3 PDF Encrypt:
Open password : a long passphrase you generated (see below)
Owner password : a different one, kept by you
Allow printing : ticked
Allow copying : unticked
Allow modifying : unticked
Allow annotations: unticked
-> merged-watermarked-encrypted.pdf (15 pages)
4 Send: the file by email, the open password by phone or instant messageThe order matters: encryption always goes last. An encrypted file needs its password to be read, and the merge, split, and watermark tools cannot supply one, so they report that the file cannot be read. Step 4 deserves emphasis too: putting the file and its password in the same email is the same as not encrypting.
Choosing a good password
- Length beats complexity: a passphrase of four or five unrelated words is usually harder to guess than a short 8-character password with symbols, and easier to remember.
- Avoid birthdays, phone numbers, and company names, which social engineering can infer.
- Do not reuse one password across files or services.
- Generate and store it in a password manager, and deliver it through a separate channel.
- The tool does not store your password and has no recovery feature: if you forget it, the file cannot be opened again. Back up the password or keep an unencrypted original somewhere safe.
Encryption versus other protections
| Method | Protects against | Does not protect against | Fits |
|---|---|---|---|
| PDF open password | Strangers opening and reading | Someone with the password forwarding or screenshotting | Sensitive files sent to specific people |
| Permission restrictions | Casual copying, printing, editing | Tools that ignore the flags | A reminder, not a security measure |
| Watermark | Tracing a leak, signalling confidentiality | Reading or copying | Combine with a password to mark ownership |
| Password-protected archive | Reading in transit | The file itself once extracted | Sending several files once |
| Cloud drive with access control | Unauthorized access | Depends on the drive provider | Collaboration |
Common problems and diagnosis
| Symptom | Cause | Fix |
|---|---|---|
| Encrypt & download is greyed out | No file chosen, or the open password is empty | Upload a file and enter an open password |
| An error while encrypting | The source already has a password, or is damaged | Remove the old password in Decrypt mode, then encrypt again |
| Decrypt says wrong password | The password is not correct | Check case and input method; the tool cannot recover passwords |
| An encrypted file fails to load in merge or split | Encrypted files need a password to be read | Decrypt first, process, then encrypt again |
| The recipient can still copy text | You allowed copying, or their software ignores the flags | Unticking only acts as a nudge; real secrecy comes from the open password |
| An old reader cannot open it | A newer algorithm was used | Use a newer reader, or confirm the actual algorithm before deciding |
| File size changes slightly after encryption | Encryption rewrites the file structure | Normal |
Document structure: do bookmarks and forms survive encryption?
Unlike merge and split, the encryption tool loads the original document, applies encryption, and saves that same document, rather than copying pages into a new one. Bookmarks, form fields, and other document-level structures should therefore usually survive. That still depends on how the library parses a particular file, so for important files check the result: are bookmarks still there, can forms be filled, does the file display correctly in the reader your recipient will use.
When not to rely on this kind of encryption
- You need regulatory compliance, such as a particular industry's requirements on algorithms and key management: use a certified enterprise solution and verify the exact algorithm.
- The password will be handed over together with the file to someone you do not trust: encryption means nothing then.
- You hope permission flags will stop the recipient copying: they cannot, they only signal intent.
- The file contains a valid digital signature: re-saving can affect it, so verify signatures separately from this workflow.
- Very large files: encryption runs in browser memory, so the larger the file the heavier it is; split it first.
Privacy
Both encrypting and decrypting happen in the browser: neither the file nor the password you type is sent to a server. You can verify it in the developer tools Network panel, where no request carrying the file or the password appears during the operation. A reminder, though: local processing guarantees that no third party is involved in transit, not that the file becomes unbreakable. Security is still decided by password strength, the encryption algorithm, and how you pass the password to the recipient.