Platform PDF annotation & page-object editing

Android can natively edit PDF annotations since API 36.1 — before that the platform story was render-only and the docs still say so: the Jetpack viewer guide's PDF surface is PdfViewerFragment, which explicitly does not support edit mode and hands annotation off to other apps via an android.intent.action.ANNOTATE intent [kb://android/develop/ui/views/layout/pdf/implement-pdf-viewer]. Do not conclude "use a third-party library" for annotation work before applying the version gate below.

The version gate (decide the entry point first)

Two parallel renderers expose the same editing surface (android.graphics.pdf.component):