BoldSignEasily embed eSignatures in your .NET applications. Free sandbox with native SDK available.
There are two types of open encrypted PDF.
1: Open the protected PDF file with the original (correct) password.
2: Try to open an encrypted PDF file without knowing the password.
1. If you want to open the PDF password without knowing the password, it is recommended to try Google Drvice, which is a free and safe method to delete the password on the PDF.
2. If you don't know the password, I suggest you try GuaPDF. It can delete any easy password from the PDF to open the encrypted PDF file.
By the way, if the password is too complicated, the most effective way is to use professional tools. In order to ensure the security of the data in the PDF file, this is the best choice. Recommend the software i have used here: