The Unlock PDF tool decrypts the file by running qpdf with the --password flag set to whatever value was typed into the form.
When qpdf fails to decrypt the file, the Unlock PDF page detects the ERR_FAILED_PROCESSING error code, clears both password fields, and returns the user to the password step to retry.
Unlock PDFUnlock PDF Wrong Password Error
Type the password into the first field and click the unlock button.
Wait for that processing indicator on screen to fully disappear before trying anything else.
Check the password field for any remaining text.
Microsoft's community advises that since Windows has no option to unlock a password-protected PDF, users should verify unlock steps with the support channel of whatever tool created or encrypted the file. How can I open or unlock PDF without password if I forgot it
Retrying After a Failed Decryption
Enter the password again in the cleared field.
Submit the form to start the decryption process.
Verifying the Unlocked File
Download the resulting PDF file.
Open the file in a PDF viewer.
Continue with Unlock PDF Requires Known Password or Unlock PDF Temp File Privacy.
Frequently Asked Questions about Unlock PDF Wrong Password Error
How do I retry the password?
Type the password into the cleared field and submit the form.
Where do I find the password field?
Look for the input box on the password step of the page.
How do I download the unlocked PDF?
Click the download link after the processing completes.
How do I check if the file opened?
Confirm no password prompt appears when the file loads.