Add note about Android exports not using PCK.

development/compiling/compiling_with_script_encryption_key.rst

@@ -22,6 +22,12 @@ with that same key.
     It is absolutely **required** to compile your own export templates to use
     PCK encryption.
 
+.. warning::
+
+    By default, Android exports store assets directly in the APK file and
+    aren't affected by PCK encryption. To use PCK encryption on Android, enable
+    **APK expansion** in the export options.
+
 Step by step
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