Why remove the password? Usually to avoid typing it every time, for archiving in a system that does not support encrypted files, or to share the document without the protection.
The process is simple: upload the encrypted PDF, enter the current password, click 'Unlock', and download the unprotected file. If the password is wrong, the operation will not complete.
Important: removing a password without knowing the original one is not possible through legitimate online tools. Services claiming to crack a protected PDF without a password either do not work or pose a security risk.