https://www.apkmirror.com/apk/adobe/adobe-sign/adobe-sign-4-0-1-release/adobe-sign-4-0-1-android-apk-download/
Just downloaded the Adobe Acrobat Sign 4.0.1 (arm64-v8a + arm-v7a) (nodpi) (Android 5.0+) APK from @APKMirror