Adding password protection and restricting editing permissions.
Third-party developers "crack" these applications to provide paid subscription features for free. In an "unlocked" version of Adobe Acrobat, you typically get access to: Modifying text and images directly on mobile. or deleting pages.
Converting scanned documents into searchable, editable text. Adobe Acrobat Reader: Edit PDF - Apps on Google Play or deleting pages.
Merging multiple files, reordering, or deleting pages. or deleting pages.