pdf-annotations

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):

Entry point	Editing available	Device requirement
PdfRenderer.Page	API 36.1+	platform release
PdfRendererPreV.Page	SDK extension 18	API 31+ with the PDF module updated (PreV itself needs extension 13)

Gate at runtime with SdkExtensions.getExtensionVersion(Build.VERSION_CODES.S) [kb://android/guide/sdk-extensions/index]. Extension 18 reaches back to API 31 via mainline updates, so PdfRendererPreV is the branch that covers most devices.

The workflow: open → edit → write

// The fd must be seekable — pipes/sockets are rejected at construction.
ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY).use { fd ->
    PdfRenderer(fd).use { renderer ->                    // or PdfRendererPreV on the ext-18 branch
        renderer.openPage(0).use { page ->
            // Only SUPPORTED annotation types are listed. The pairs are
            // android.util.Pair — NO Kotlin destructuring (no component1/2);
            // read them with .first / .second.
            val existing = page.getPageAnnotations()
            val staleId: Int? = existing.firstOrNull { it.second is FreeTextAnnotation }?.first

            val highlight = HighlightAnnotation(boundsList)   // List<RectF> quads
            val id = page.addPageAnnotation(highlight)
            check(id != -1) { "annotation rejected" }         // add returns -1, it does NOT throw

            highlight.color = newColor
            page.updatePageAnnotation(id, highlight)          // by id -> Boolean success
            staleId?.let { page.removePageAnnotation(it) }    // by id, not list position
        }
        // Write BEFORE close(), to a separate writable fd; the boolean is
        // removePasswordProtection (IOException if true and the doc stays encrypted).
        ParcelFileDescriptor.open(
            dest,
            ParcelFileDescriptor.MODE_READ_WRITE or ParcelFileDescriptor.MODE_CREATE,
        ).use { out ->
            renderer.write(out, false)
        }
    }
}