How can I open a password protected PDF file?

Hi @Reachel5FB4 

Hope you are doing well!

When we are dealing with password protected files, the primary resolution is to get the password from the creater in order to open the document. 

To change or remove the password for an existing protected PDF, you would be required Acrobat DC desktop application. You can change/remove password security, only when these conditions are met:  https://community.adobe.com/t5/acrobat/how-to-mange-your-document-passwords-with-acrobat-dc/td-p/110...

However, Adobe Acrobat Reader mobile app allows you to protect your PDF file with a password. Subscribers to Adobe Acrobat Premium or Adobe Acrobat Pro DC can password protect PDFs by setting a document open password.

Note: Only document open passwords can be set up using the mobile app. For permission password, you would be required Acrobat DC desktop application.

For more help : https://community.adobe.com/t5/acrobat-reader-mobile/you-can-now-password-protect-pdf-using-adobe-ac...

Regards,

Ria