There are two very different types of PDF password protection, and whether you can remove one depends on which type it is — and whether you know the password. Understanding the difference clarifies what's actually possible.
Two Types of PDF Password Protection
An open password (user password) prevents anyone from opening the file without entering the correct password. A permissions password (owner password) allows the file to be opened by anyone but restricts specific actions — printing, copying, editing. A PDF can have one, both, or neither.
These are fundamentally different situations. Removing a permissions password to restore copy or print access is much easier than bypassing an open password that prevents you from seeing the content at all.
If You Know the Password: Easy
If you have the password — either the open password to access the file or the owner password to change permissions — removing protection is straightforward. In Adobe Reader: open the file with the password, go to File → Properties → Security, change the Security Method to "No Security," and save. In Preview on Mac: open with the password, go to File → Export as PDF, and the exported file won't carry the password. In Chrome: open the password-protected PDF, enter the password, then print to PDF — the resulting PDF has no password.
WukongPDF's Unlock PDF tool handles this as well: upload the file, enter the password, and download an unprotected version. This is particularly useful when the document needs to be processed by other tools that don't support password entry.
Permissions-Only PDFs: Often Bypassed
PDFs with permissions restrictions (copy disabled, printing disabled) but no open password can be opened by anyone. The restrictions are enforced by the PDF viewer — but not by all viewers, and the enforcement is not cryptographically guaranteed the way open-password protection is.
Printing such a PDF to a PDF printer (Microsoft Print to PDF on Windows, Print → Save as PDF on Mac) creates a new, unrestricted PDF because the virtual printer driver receives the rendered output and creates a fresh file with no permissions carried over. This bypasses restrictions on documents you have a right to access — appropriate for your own documents or documents where restrictions were set unnecessarily.
Without the Password: Much Harder
A PDF with a strong open password that you don't know cannot be unlocked by any free tool through legitimate means. Strong AES-256 encryption is computationally infeasible to brute-force with consumer hardware. If you've lost a password to your own document, the options are: try password recovery software that works through common passwords and variations (effective if the password was simple), or contact the document sender for a new copy.
Older PDFs that used 40-bit or 128-bit RC4 encryption (the format before AES-256) are more vulnerable to recovery tools. Modern PDFs with AES-256 are effectively uncrackable without the password. If you're on the receiving end of a password-protected PDF and don't have the password, asking the sender is the only practical path.