Why does my PDF open fine but refuse to print?

Because it carries an owner password rather than an open password. The two are different layers. An open password stops the document being decrypted at all; an owner password leaves it readable but sets permission flags telling readers to grey out printing, copying or editing. A file can have one, both or neither, which is why a document you can read perfectly may still block the print button.

How are PDF permissions actually stored?

As a single 32-bit signed integer called /P inside the file's encryption dictionary. Each action has a bit, and a bit that is set to 1 means the action is allowed, so restrictions are recorded as zeros rather than ones. Printing is bit 3, worth 4; editing is bit 4, worth 8; copying is bit 5, worth 16; adding comments is bit 6, worth 32. Higher bits cover form filling, screen-reader access, page assembly and high-quality printing.

If permissions are just flags, what enforces them?

The reader application, voluntarily. Nothing in the file prevents a program from ignoring the flags, because the page content is decrypted before any permission is checked. Adobe Acrobat, Preview and browser viewers all honour the flags by convention. This is why removing a permissions restriction is a routine operation while removing an open password is not: one is a request, the other is real cryptography.

Which PDF encryption is strong and which is not?

The PDF standard defines four security handlers. Revision 2 uses 40-bit RC4, a keyspace of about 1.1 trillion that is brute-forceable and should be treated as obsolete. Revision 3 uses 128-bit RC4 and revision 4 uses 128-bit AES. Revision 5 and later use 256-bit AES, which is the strongest the format offers and the right choice for anything confidential.

Can a browser tool crack a PDF password I do not know?

No, and you should be sceptical of anything claiming otherwise. Removing an owner password is possible because the file is already decrypted in front of you. Recovering an unknown open password would mean breaking AES, which is not feasible. If a PDF asks for a password before it will display anything, you have to supply that password, so you can only unlock documents you already have access to.

Why did compressing my PDF make the text unselectable?

Because four of the five compression presets rasterize the pages. They re-render each page as a JPEG at a reduced resolution and rebuild the document from those pictures, so the text layer stops existing and the words become pixels. Only the Keep text preset avoids this, re-saving the file with compact object streams instead. If searchable text matters, choose that preset.

What is flattening a PDF and when do I need it?

Flattening bakes interactive elements into the page so they can no longer be changed. Filled form fields become ordinary text, comments and highlights become part of the artwork, and signatures stop being editable objects. Use it when sending a completed form so the recipient sees fixed values, or when a printer renders your annotations incorrectly. It cannot be undone, so keep the original.

Why will a tool not edit my encrypted PDF?

Encryption blocks structural edits, so merging, splitting, rotating, deleting or reordering pages all fail on a locked file. The fix is order of operations: lift the restriction first, then perform the edit, and re-protect the result afterwards if it still needs a password. Dynamic XFA forms, which store their layout as XML rather than page content, also resist editing and need printing to a fresh PDF first.

Why Will My PDF Not Let Me Print or Copy?

Short answer

A PDF can carry two different passwords. An open password encrypts the document so it cannot be read at all. An owner password leaves it perfectly readable and instead sets permission flags asking your reader to grey out printing, copying or editing. If the file opened without prompting you, it is the second kind — and that layer is a request, not a lock.

Key takeaways

Permissions live in one 32-bit integer called /P. A bit set to 1 means allowed, so restrictions are stored as zeros.
Printing is bit 3 (value 4), editing bit 4 (8), copying bit 5 (16), comments bit 6 (32). Four more bits were added in later revisions.
Nothing enforces those flags except your reader's goodwill: page content is decrypted before permissions are ever checked.
The four standard handlers are RC4-40, RC4-128, AES-128 and AES-256. RC4-40 has about 1.1 trillion possible keys and is obsolete; AES-256 is the one to use.
Four of the five compression presets rasterize your pages, destroying selectable text. Only Keep text leaves the text layer intact.
An A4 page at the default 120 DPI is 1.39 million pixels; at print-standard 300 DPI it is 8.70 million — 17.4 times more.

What are the two PDF passwords?
How are permissions actually stored?
What stops someone ignoring the flags?
Which encryption does my file use?
Why edits fail on a locked file
The lock people create by accident
What resolution should a rasterized page be?
Flattening: the deliberate one-way lock
Five rules for locked documents
Terms worth knowing
All 16 tools in this guide

What are the two PDF passwords?

Almost every confusing thing about locked PDFs comes from one fact: the format defines two independent passwords, they do very different jobs, and most software calls them both "password".

The open password (the specification calls it the user password) controls decryption. Without it the bytes of every page are unreadable, and no software can display anything. This is genuine cryptography and there is no way around it.

The owner password (also called the permissions password) controls what a reader is allowed to do once the document is on screen. A file with only an owner password opens instantly for everyone, shows every page, and greys out whichever buttons the flags say to grey out. That is the situation almost everyone means by "my PDF is locked".

The order matters. On the right the document is already decrypted by the time anything looks at the permission flags, which is the whole reason that layer can be lifted.

Unlock PDF (Owner-Password Removal) → The anchor tool for this guide. It reads the security dictionary inside your file and reports what it finds — the encryption scheme, the revision number, whether an open password is required, and a row per permission showing allowed or blocked — before changing anything. It removes owner and permissions passwords; it does not crack or guess unknown open passwords.

How are permissions actually stored?

Not as a list of rules. As a single signed 32-bit integer named /P, sitting in the file's encryption dictionary. Each restrictable action owns one bit, and here is the part that catches people out: a bit set to 1 means the action is allowed. Restrictions are absences. A heavily locked document has a /P value full of zeros.

The permission bits, numbered as in the PDF specification
Action	Bit	Decimal value	Available from
Printing	3	4	Revision 2
Editing the content	4	8	Revision 2
Copying text and images	5	16	Revision 2
Adding comments	6	32	Revision 2
Filling in forms	9	256	Revision 3
Screen-reader access	10	512	Revision 3
Extracting and reordering pages	11	1024	Revision 3
High-quality printing	12	2048	Revision 3

You can read a value directly. Take a document whose flags allow copying and comments but block everything else: 16 + 32 = 48, plus the reserved high bits the format requires to be set. Allow printing as well and it becomes 52. This is why a scanned bank statement will let you print but not select a single word, while a shared report does the exact opposite — two different integers, produced by two different export settings.

Why old files show fewer switches: revision 2 — 40-bit RC4 — only defines bits 3 to 6. Form filling, screen-reader access, page assembly and high-quality printing did not exist yet, so in a revision 2 file those higher bits hold reserved values and mean nothing. A tool that displayed them anyway would be showing you noise.

What stops someone ignoring the flags?

Nothing does. That is not a defect in any particular tool, it is how the format works.

Follow the sequence in the diagram above. The reader decrypts the page content, then looks at /P to decide which menu items to disable. By the time the permission check happens the text is already sitting decrypted in memory. Honouring the flags is a convention that Adobe Acrobat, Preview, Chrome and Edge all follow, and any program is free not to.

This explains the asymmetry that makes people suspicious of unlocking tools. Removing an owner password is routine because the content was never protected from you in the first place. Recovering an unknown open password would mean defeating AES, which is not something a web page can do — and any site claiming to is worth closing.

The practical consequence for anyone choosing protection: permission flags are a courtesy, encryption is a control. If a document genuinely must not be read by the wrong person, it needs an open password. If you only want to discourage casual printing of a draft, flags are the right amount of friction and nothing more.

Protect PDF → Encrypts with 256-bit AES in your browser, so neither the file nor the password is uploaded. The optional permissions panel restricts printing (including a low-resolution-only setting), copying, editing, commenting and form filling, enforced with a separate owner password. Screen-reader access is deliberately left enabled. Up to 30 files per batch share one password and download as a single ZIP.

Which encryption does my file use?

The PDF standard has accumulated four security handlers over its life, and the gap between the oldest and newest is enormous. The revision number in a file's encryption dictionary tells you which one you have.

The four standard security handlers and what each is worth today
Revision	Cipher	Key length	Possible keys	Verdict
2	RC4	40-bit	about 1.1 trillion	Obsolete, brute-forceable
3	RC4	128-bit	3.4 × 10³⁸	Legacy; cipher itself now deprecated
4	AES	128-bit	3.4 × 10³⁸	Sound
5 and later	AES	256-bit	1.2 × 10⁷⁷	Strongest the format defines

A 40-bit keyspace sounds astronomical until you compare it with the others: 2⁴⁰ is roughly 1.1 × 10¹², a number ordinary hardware can work through. Revision 2 files still turn up regularly because old scanners, photocopiers and statement generators were configured decades ago and nobody revisited the setting. If you find one protecting anything sensitive, re-encrypt it at AES-256.

Why edits fail on a locked file

Encryption does not only stop reading. It stops writing too, because a tool cannot rewrite a document structure it cannot fully parse. So every page operation fails on a locked file, usually with an unhelpful error.

The fix is always the same three-step order, and it is worth internalising because it turns a dead end into a routine job:

Lift the restriction. Remove the owner password to get an unrestricted working copy.
Do the actual edit. Merge PDF, Split PDF, Rotate PDF, Delete PDF Pages, Reorder PDF Pages, PDF Page Extractor or Add Page Numbers to PDF all work normally once the file is unrestricted.
Re-protect if it still needs it. Encrypt the result at AES-256 and, if you are setting permissions, give the owner password a different value from the open password. If they match, anyone who can open the file can also lift its restrictions, which makes the permissions decorative.

That last detail is easy to get wrong and quietly undoes the whole exercise.

The lock people create by accident

The other half of "why can't I do this with my PDF" has nothing to do with passwords. It is self-inflicted, and it happens during compression.

There are two completely different ways to make a PDF smaller. One re-saves the document with compact object streams: the text layer survives, words stay selectable and searchable, and the saving is modest. The other re-renders every page as a JPEG at a reduced resolution and builds a new document out of those pictures. That shrinks the file dramatically — and turns every word into pixels.

Compression presets: what each one does to the text layer
Preset	Method	Resolution	JPEG quality	Text stays selectable
Keep text	Compact re-save	unchanged	not applicable	Yes
Light	Rasterize	150 DPI	85%	No
Balanced (default)	Rasterize	120 DPI	72%	No
Strong	Rasterize	96 DPI	60%	No
Smallest	Rasterize	72 DPI	50%	No

Four of the five rasterize, including the recommended default. Nothing is hidden — the preset descriptions say so — but the consequence only becomes obvious later, when the document will not respond to a text search, a screen reader finds nothing to read, and PDF to Text Extractor returns an empty result. At that point the words are pictures and no amount of re-processing brings them back. This is a genuine one-way door, more permanent than any password.

So the decision is not "how small do I want it" but "does anyone need to search, select or read this aloud". If yes, use Keep text and accept a smaller saving. If it is a scanned receipt nobody will ever search, rasterize freely.

Compress PDF → Five presets from Keep text to Smallest, with a live size estimate sampled from your own files before you commit. The Advanced panel exposes the resolution directly, from 48 to 200 DPI, plus the JPEG quality and an optional grayscale mode for scans. Up to 30 files per batch share one setting.

What resolution should a rasterized page be?

Once you have decided to rasterize, DPI is the only lever that matters, and its effect on size is quadratic rather than linear: doubling the resolution quadruples the pixel count. Here is what each preset actually produces for a standard A4 page.

Pixels in one A4 page (8.27 × 11.69 in) at each resolution
Resolution	Page in pixels	Megapixels	Relative to 72 DPI	Typical use
72 DPI	595 × 842	0.50 MP	1.0×	Screen-only scans
96 DPI	794 × 1123	0.89 MP	1.8×	Email attachments
120 DPI	992 × 1403	1.39 MP	2.8×	Balanced default
150 DPI	1240 × 1754	2.18 MP	4.3×	Readable when zoomed
200 DPI	1654 × 2338	3.87 MP	7.7×	Light printing
300 DPI	2480 × 3508	8.70 MP	17.4×	Print standard

The default sits near the bottom of the range. That is the right trade for on-screen reading and the wrong one for anything destined for paper.

If you are working the other way — you have an image and need to know what it can print at, or you have a print size and need the resolution — the calculator below runs the same arithmetic.

Print Size & Resolution Calculator

Flattening: the deliberate one-way lock

Flattening is the one irreversible change you might actually want. It bakes interactive elements into the page: filled form fields become ordinary text, comments and highlights become part of the artwork, and nothing can be edited afterwards.

Two situations call for it. Sending a completed form, where you want the recipient to see fixed values rather than editable boxes they might disturb. And printing annotated documents, where some printers render comment markup wrongly or drop it entirely — flattening makes the annotation part of the page so it prints exactly as displayed.

Two kinds of file resist it. Encrypted documents cannot be modified at all, so the restriction must come off first. Dynamic XFA forms, an Adobe LiveCycle format that stores its layout as XML rather than as page content, are not really PDF pages underneath; the usual route is to print one to a fresh PDF and flatten that copy.

PDF Flatten Tool → Bakes form fields and annotations into the page, with a rasterize mode offering 96, 150, 200 or 300 DPI when a document needs to be made completely non-interactive. It detects signed, encrypted and XFA documents up front and tells you which of them it cannot process, instead of producing a broken file.

Five rules for locked documents

Find out which lock you have before doing anything. If the file opened without a prompt, no cryptography is standing in your way — only flags.
Unlock first, edit second, re-protect last. Every page operation fails on an encrypted file, and fighting that order wastes more time than following it.
Give the owner password a different value from the open password. Identical passwords make the permission flags meaningless to anyone who can open the document.
Choose Keep text unless you are certain nobody needs to search the document. Rasterizing is permanent in a way passwords never are.
Use AES-256 for anything confidential, and re-encrypt anything you find at RC4-40. A 40-bit key is not protection in 2026.

Terms worth knowing

Open password (user password): The password required to decrypt and display the document. Without it, no software can show anything.
Owner password (permissions password): The password that guards the permission settings. The document opens without it; it only controls who may change the restrictions.
/P: The 32-bit signed integer holding the permission bits. A set bit means allowed, so restrictions appear as zeros.
Encryption dictionary: The section of a PDF describing how it is protected: cipher, key length, revision and the /P value. It is stored unencrypted, because a reader must read it before it can decrypt anything.
Security handler revision: A number from 2 upwards identifying which generation of PDF encryption a file uses. It determines both the cipher and which permission bits are meaningful.
Rasterize: Replacing page content with a picture of that page. Makes files smaller and permanently removes selectable text.
Text layer: The actual characters stored in a PDF, as distinct from their appearance. Searching, selecting, copying and screen readers all depend on it.
Flattening: Merging interactive elements such as form fields and annotations into the static page so they can no longer be edited.
XFA form: An XML-based Adobe form format carried inside a PDF wrapper. Standard PDF tools cannot edit or flatten it directly.
DPI: Dots per inch. Because it applies in both directions, pixel count rises with the square of the number.

All 16 tools in this guide

Unlock PDF (Owner-Password Removal)Read the security dictionary, then lift permission restrictions Protect PDFEncrypt with AES-256 and set owner permissions Compress PDFFive presets, from lossless re-save to heavy rasterizing PDF Flatten ToolBake form fields and annotations into the page Merge PDFCombine several documents into one file Split PDFBreak one document into separate files PDF Page ExtractorPull out just the pages you need Delete PDF PagesRemove pages by number or range Reorder PDF PagesRearrange pages into a new order Rotate PDFFix sideways or upside-down scans Add Page Numbers to PDFStamp numbering with position, size and colour PDF to Text ExtractorPull the text layer out as plain text PDF Word CounterCount words without opening an editor PDF to JPGTurn pages into images at a chosen quality JPG to PDFBuild a document from photos or scans Print Size & Resolution CalculatorConvert between pixels, print size and DPI

Authoritative sources

Last updated: 2026-08-25 · Published: 2026-08-25 · Written by the miniwebtool.com editorial team.

This guide is for general and educational use. It describes how the PDF format's own security features work and how to lift restrictions on documents you already have lawful access to. It is not advice on circumventing access controls, and removing protection from material you do not have the right to use may breach copyright or computer-misuse law where you live. Encryption settings and preset values describe current tool behaviour and may change.