The most popular way to lock PDFs and apply restrictions (stop printing, editing, etc.) is to use passwords. However, users can share passwords and therefore locked PDFs with others. And passwords and PDF restrictions can be easily removed with PDF password removal software. So passwords are not a secure way to lock PDF files.
If you want to lock PDF files against unauthorized use and also control how they are used, then you need PDF DRM software. PDF DRM enables you to lock PDFs to devices so they cannot be shared and prevents users from editing, copying, printing and screen grabbing content.
Infographic by – Locklizard