The Limits of Static Documentation
A released PDF can be accurate, searchable and appropriate for its audience. Problems arise when teams cannot identify its revision, maintain copied content consistently or help users select the correct product variant. Those are lifecycle and information-design problems, not simply consequences of a file format.
A fixed document may also be the best delivery method for a particular requirement. Keep it where users need a complete manual or offline reference, and connect it to the same controlled source and release process as other channels.
