android/app/src/main/res/layout/activity_consent_pdf_viewer...

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/ConstraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="uprrp.tania.activities.ConsentPdfViewerActivity">


    <com.github.barteksc.pdfviewer.PDFView
        android:id="@+id/pdf_viewer"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/appBarLayout">

    </com.github.barteksc.pdfviewer.PDFView>

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="61dp"
        android:theme="@style/Theme.MarleApp.AppBarOverlay"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/Theme.MarleApp.PopupOverlay" />

    </com.google.android.material.appbar.AppBarLayout>


</androidx.constraintlayout.widget.ConstraintLayout>