How to add or remove pages from a password protected PDF file?

Hello Friends,

Hi there! I am trying to add and remove pages from a data sheet from one of our vendors, but is password protected and I can't add or remove pages. In this situation I need to add additional pages to document the specs and buy parts, but I can't edit it without the password and the vendor won't give us the password. So, any idea or suggestion how to add or remove pages from a password protected pdf document?

Thank You
Vicky Milza