Open document activity in separate task.
diff --git a/app/src/main/java/com/artifex/mupdf/viewer/app/LibraryActivity.java b/app/src/main/java/com/artifex/mupdf/viewer/app/LibraryActivity.java
index a4c449f..aed4aba 100644
--- a/app/src/main/java/com/artifex/mupdf/viewer/app/LibraryActivity.java
+++ b/app/src/main/java/com/artifex/mupdf/viewer/app/LibraryActivity.java
@@ -45,6 +45,7 @@
 			if (data != null) {
 				Intent intent = new Intent(this, DocumentActivity.class);
 				intent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT);
+				intent.addFlags(Intent.FLAG_ACTIVITY_MULTIPLE_TASK);
 				intent.setAction(Intent.ACTION_VIEW);
 				intent.setDataAndType(data.getData(), data.getType());
 				startActivity(intent);