PDFGym
EN

Protect a PDF with a password

or drop one here

Password protection

Require a password whenever this PDF is opened.

Uses PDF 1.7 AES-128. PDF/A files stay archival and are not encrypted.

Choose a PDF file first.

Choose a PDF, enter a new password of at least 6 characters twice, and download a locked copy with -protected in its name. The file is encrypted with AES-128 inside this browser tab, then reopened with your password and checked page by page before the download appears. Archival PDF/A files are refused, because encryption would break their format.

The offer letter going out by email

This page locks files that must travel: an offer letter, a medical report, a contract draft. Anyone without the password sees scrambled bytes; anyone with it reads the same pages you locked.

Say HR must email Offer-Novak-Q4.pdf to a candidate on Friday afternoon, salary and bonus on page two. You open it here, leave Protect selected, type a 16 character phrase into New password, repeat it in Confirm password, and press Protect PDF. Offer-Novak-Q4-protected.pdf downloads; the file goes by email, the phrase by text message, and a leaked inbox exposes nothing readable.

An open password is real encryption, not a flag: the content is scrambled with a key derived from your password, and no reader draws a page without unwrapping it. This page writes AES-128 under PDF 1.7, the widely supported middle ground every mainstream reader opens. The reopen check proves the locked file refuses to open without the password, opens with it, and holds the same pages and text.

The password is the whole lock, so treat it like one: long and unique beats clever and short, and it must travel separately from the file. The 6 character minimum is a floor, not advice; a full sentence you can say over the phone survives both guessing and forgetting.

Four steps from open file to locked copy

  1. Choose a PDF

    Press Choose a PDF or drop the file onto the page. One file per run; merge several first when the bundle must share one password.

  2. Leave Protect selected

    Protect is selected when this page opens. An already locked file stops here with This PDF is already protected. Choose Unlock instead.

  3. Enter the new password

    Type at least 6 characters into New password and repeat them in Confirm password. Mismatched entries keep the run disabled until both boxes agree.

  4. Protect and download

    Press Protect PDF. The locked file is reopened with your password and checked before Download protected PDF appears.

Locks that fail, and passwords that vanish

The two password boxes must match exactly, and the minimum is 6 characters: short or mismatched entries disable the run with an explanation under the button. Retype slowly; password boxes hide typos by design.

Archival PDF/A files are refused outright, because encryption would break the archival format. Export a regular PDF first, then lock that copy. Files already carrying a password stop with a note to choose Unlock instead; unlock, then relock with the new phrase.

A forgotten password has no recovery path here or anywhere honest: without it the file stays scrambled bytes. Store the phrase in a password manager before you close the tab, and test the download by opening it once yourself.

When a password is the wrong protection

A password guards access, not content: the recipient you trust still sees every page, including the metadata, the edit history and the paragraphs you meant to cut. Redact first with Redact PDF, scrub the traces with Remove PDF metadata, then lock the cleaned copy.

The two password kinds side by side:

Open password versus permissions flags
What you wantOpen passwordPermissions flag
Strangers cannot open itYes, encryptedNo, the file opens
Printing can be blockedYes, nothing opens to printOnly if the reader obeys
Survives a different readerYesNo
Offered on this pageYesNo, deliberately

Permissions style no-print flags are not offered here, deliberately: readers may ignore them, and any tool that opens the file clears them. When the file must truly stay closed to some eyes, an open password is the only layer that works. To remove a lock instead of adding one, Unlock PDF takes the same file back.

Short answers about locking PDFs

How long should the password be?
At least the 6 characters the tool demands, but aim for a full phrase of 16 or more. Length beats complexity: three random words outlast one clever abbreviation.
Can I lock several files with one password?
One file per run here. Merge the set first with Merge PDFs, then protect the combined file once.
Will the recipient's reader ask for the password?
Yes. AES-128 under PDF 1.7 opens in every mainstream reader, each of which prompts before drawing the first page. Test the download in a second reader when the recipient matters.
Does locking change the pages?
No. Only the encryption layer is added; pages, text and layout stay identical. The reopen check compares all three with the source before download.
Can I add a no-printing rule instead?
No. Permission flags are advisory and many readers ignore them, so this page does not write them. An open password is the only lock offered.

More tools, same tab, same checks

Everything below runs in the browser with no account and reopens its own output before the download. Scrub and redact first, lock here, then send.