diff --git a/README.md b/README.md
index d9a5e79..b6cf2fd 100644
--- a/README.md
+++ b/README.md
@@ -163,8 +163,9 @@ A few notes:
 - For text, please use `DocumentTextView`: it will notify the parent when it gets bigger.
 - For editable text, please use `DocumentEditText`: same as above.
 - If using app compat, you might want to use the `AppCompat-` version of these widgets.
-- We can't split text of a single view into multiple pages or columns. 
+- We can't split text of a single view into multiple pages or columns (for now).
   It is your responsibility to have Views that are small enough to avoid blank spaces.
+- For custom views, take a look at `DocumentHelper` methods.
 
 To enable columns, use `document.setColumnsPerPage(int)` or the XML attribute `app:columnsPerPage`.
 
@@ -230,7 +231,10 @@ You must have appropriate permissions to write the file in that location.
 On Marshmallow+, these permissions must be explicitly asked to the user.
 
 The library currently will automatically ask the `READ_EXTERNAL_STORAGE` and `WRITE_EXTERNAL_STORAGE`
-permissions (this can be improved though). Make sure you implement `onRequestPermissionResult`:
+permissions if the output file appears to be in the external storage. Make sure you
+
+- declare these permissions in your manifest
+- implement `onRequestPermissionResult` as such:
 
 ```java
 @Override
diff --git a/demo/src/main/AndroidManifest.xml b/demo/src/main/AndroidManifest.xml
index 22396bc..a325af8 100644
--- a/demo/src/main/AndroidManifest.xml
+++ b/demo/src/main/AndroidManifest.xml
@@ -2,6 +2,9 @@
 <manifest package="com.otaliastudios.printer.demo"
           xmlns:android="http://schemas.android.com/apk/res/android">
 
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
+
     <application
         android:allowBackup="true"
         android:icon="@drawable/logo_48dp"
diff --git a/library/src/main/AndroidManifest.xml b/library/src/main/AndroidManifest.xml
index f7a0710..dbfefab 100644
--- a/library/src/main/AndroidManifest.xml
+++ b/library/src/main/AndroidManifest.xml
@@ -2,9 +2,6 @@
     package="com.otaliastudios.printer"
     xmlns:android="http://schemas.android.com/apk/res/android">
 
-    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
-    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
-
     <application
         android:allowBackup="true"
         android:supportsRtl="true"/>
diff --git a/library/src/main/java/com/otaliastudios/printer/BitmapPrinter.java b/library/src/main/java/com/otaliastudios/printer/BitmapPrinter.java
index a6ff9b5..e3d2d38 100644
--- a/library/src/main/java/com/otaliastudios/printer/BitmapPrinter.java
+++ b/library/src/main/java/com/otaliastudios/printer/BitmapPrinter.java
@@ -100,11 +100,11 @@ public void setPrintScale(int maxWidth, int maxHeight) {
     @Override
     public void print(final String printId, @NonNull final File directory, @NonNull String filename) {
         Context context = mDocument.getContext();
-        if (!checkPermission(context)) return;
+        if (!checkPermission(context, directory)) return;
         if (!checkPreview(printId, directory, filename)) return;
 
         if (filename.toLowerCase().endsWith(mFormat)) {
-            filename = filename.substring(0, filename.length() - 4);
+            filename = filename.substring(0, filename.length() - mFormat.length());
         }
         if (mDocument.getPageCount() == 0) return;
 
diff --git a/library/src/main/java/com/otaliastudios/printer/Container.java b/library/src/main/java/com/otaliastudios/printer/Container.java
index dae30ea..54d450c 100644
--- a/library/src/main/java/com/otaliastudios/printer/Container.java
+++ b/library/src/main/java/com/otaliastudios/printer/Container.java
@@ -110,9 +110,8 @@ interface Container<Root extends Container, Child extends Container> {
      * - check if {@code child} can get some views from the next child
      *
      * @param child the container notifying us
-     * @param space the available space
      */
-    void onSpaceAvailable(Child child, int space);
+    void onSpaceAvailable(Child child);
 
     /**
      * Our child notifies that he has no more space, and some of the views would actually
diff --git a/library/src/main/java/com/otaliastudios/printer/DocumentColumn.java b/library/src/main/java/com/otaliastudios/printer/DocumentColumn.java
index 732dceb..5437b40 100644
--- a/library/src/main/java/com/otaliastudios/printer/DocumentColumn.java
+++ b/library/src/main/java/com/otaliastudios/printer/DocumentColumn.java
@@ -27,7 +27,7 @@ class DocumentColumn extends LinearLayout implements Container<DocumentPage, Doc
 
     private int mWidthBound;
     private int mHeightBound;
-    private int mAvailableSpace;
+    private int mContentHeight;
     private int mColumnNumber;
 
     DocumentColumn(@NonNull Context context, int number, int widthBound, int heightBound) {
@@ -49,7 +49,6 @@ int getNumber() {
     void setBounds(int widthBound, int heightBound) {
         mWidthBound = widthBound;
         mHeightBound = heightBound;
-        mAvailableSpace = mHeightBound;
     }
 
     boolean isBounded() {
@@ -88,7 +87,7 @@ public boolean contains(View view) {
     }
 
     @Override
-    public void onSpaceAvailable(DocumentColumn child, int space) {
+    public void onSpaceAvailable(DocumentColumn child) {
         // We have no children so no one can call this.
     }
 
@@ -201,31 +200,32 @@ private int getCurrentHeight() {
     /**
      * Something changed here.
      * - did it grow? Do nothing. Due to measuring, we don't let anyone grow beyond the page size.
-     * - did it shrink and is the first? See if previous child wants it.
-     * - did it shrink? See if we should accept a view from the next child.
+     * - did it shrink? Notify we have space available.
      */
     @Override
     public void onLayoutChange(View view, int left, int top, int right, int bottom,
                                int oldLeft, int oldTop, int oldRight, int oldBottom) {
-        int oldHeight = oldBottom - oldTop;
-        int newHeight = bottom - top;
-        mAvailableSpace = mHeightBound - newHeight;
+        // Our LayoutParams have a fixed height, see DocumentPage.
+        // So we are not going to grasp anything meaningful from bottom - top.
+        int oldHeight = mContentHeight;
+        int newHeight = getCurrentHeight();
+        int space = mHeightBound - newHeight;
         final int pn = getRoot().getNumber();
-        mLog.v("onLayoutChange:", "page:", pn, "oldHeight:", oldHeight, "newHeight:", newHeight, "avSpace:", mAvailableSpace);
+        mLog.v("onLayoutChange:", "page:", pn, "oldHeight:", oldHeight, "newHeight:", newHeight, "space:", space);
 
+        mContentHeight = newHeight;
         if (oldHeight == 0) return; // First pass.
         if (newHeight == oldHeight) return; // Not really changed. This happens.
         if (newHeight > oldHeight) return; // Nothing to do, hope we get calls to notifyTooSmall.
-        if (mAvailableSpace <= 0) return;
+        if (space <= 0) return;
 
         // Go out of the layout pass, it's not safe to pass views around during layout,
         // even if you use addViewInLayout or removeViewInLayout.
-        final int availableSpace = mAvailableSpace;
         post(new Runnable() {
             @Override
             public void run() {
                 mLog.i("onLayoutChange:", "page:", pn, "dispatching onSpaceAvailable.");
-                getRoot().onSpaceAvailable(DocumentColumn.this, availableSpace);
+                getRoot().onSpaceAvailable(DocumentColumn.this);
             }
         });
     }
diff --git a/library/src/main/java/com/otaliastudios/printer/DocumentTextHelper.java b/library/src/main/java/com/otaliastudios/printer/DocumentHelper.java
similarity index 56%
rename from library/src/main/java/com/otaliastudios/printer/DocumentTextHelper.java
rename to library/src/main/java/com/otaliastudios/printer/DocumentHelper.java
index c9f349b..bbdca1a 100644
--- a/library/src/main/java/com/otaliastudios/printer/DocumentTextHelper.java
+++ b/library/src/main/java/com/otaliastudios/printer/DocumentHelper.java
@@ -9,32 +9,42 @@
 import com.otaliastudios.printer.view.DocumentTextView;
 
 /**
- * Static utilities for text containers that might become smaller than they would like to,
- * without notifying the parent.
+ * Static utilities for views that might become smaller than they would like to,
+ * without notifying the parent. In that case we want to move them to the next page, for example.
  *
- * It is recommended that they call {@link #onLayout(View)} here to have our splitting
- * policy working.
+ * It is recommended that these views call {@link #onLayout(View)} to let us determine if they would
+ * like to be bigger, or {@link #onSpaceOver(View)} if they have already determined that.
  *
- * @see DocumentTextView
- * @see DocumentEditText
  */
-public class DocumentTextHelper {
+public class DocumentHelper {
 
-    private final static String TAG = DocumentTextHelper.class.getSimpleName();
+    private final static String TAG = DocumentHelper.class.getSimpleName();
     private final static PrinterLogger LOG = PrinterLogger.create(TAG);
 
+    /**
+     * To be called after the View has been laid out. If the view is presumably to small,
+     * this will call {@link #onSpaceOver(View)} for you.
+     *
+     * @param view The view that has been laid out
+     */
     public static void onLayout(View view) {
         if (view.getLayoutParams().height == ViewGroup.LayoutParams.WRAP_CONTENT) {
-            LOG.i("onLayout:", "We are wrap content. Looking if we can scroll.");
             // TODO: don't do this if getMaxLines is >= 0 (< MAX_VALUE). Same for getMaxheight.
             if (view.canScrollVertically(-1) || view.canScrollVertically(1)) {
                 LOG.w("onLayout:", "We can scroll. Notifying the parent column.");
-                notifyContainer(view);
+                onSpaceOver(view);
             }
         }
     }
 
-    private static void notifyContainer(View view) {
+    /**
+     * Notifies the {@link DocumentView} that this view would like to be bigger than
+     * it actually is. This might trigger a re-layout, for example moving the view to the
+     * next page.
+     *
+     * @param view The view that would like to be bigger
+     */
+    public static void onSpaceOver(View view) {
         Container<?, ?> container = null;
         View current = view;
         while (true) {
diff --git a/library/src/main/java/com/otaliastudios/printer/DocumentPage.java b/library/src/main/java/com/otaliastudios/printer/DocumentPage.java
index 419af5f..98a8570 100644
--- a/library/src/main/java/com/otaliastudios/printer/DocumentPage.java
+++ b/library/src/main/java/com/otaliastudios/printer/DocumentPage.java
@@ -266,7 +266,7 @@ public boolean contains(View view) {
     }
 
     @Override
-    public void onSpaceAvailable(DocumentColumn child, int space) {
+    public void onSpaceAvailable(DocumentColumn child) {
         Utils.clearUntakableView(child);
         mLog.i("onSpaceAvailable:", "fromColumn:", child.getNumber());
 
@@ -286,9 +286,7 @@ public void onSpaceAvailable(DocumentColumn child, int space) {
             DocumentColumn next = mColumns.get(which + 1);
             while (tryPassFirstViewToPrevious(next, child)) {} // try until it stops
         } else {
-            // TODO: the 'space' value at this point might not be meaningful
-            // (might be bigger if we gave something to previous column). But it's unused
-            getRoot().onSpaceAvailable(this, space);
+            getRoot().onSpaceAvailable(this);
         }
     }
 
diff --git a/library/src/main/java/com/otaliastudios/printer/DocumentPager.java b/library/src/main/java/com/otaliastudios/printer/DocumentPager.java
index d6fccec..df7027c 100644
--- a/library/src/main/java/com/otaliastudios/printer/DocumentPager.java
+++ b/library/src/main/java/com/otaliastudios/printer/DocumentPager.java
@@ -318,7 +318,7 @@ public boolean contains(View view) {
     }
 
     @Override
-    public void onSpaceAvailable(DocumentPage child, int space) {
+    public void onSpaceAvailable(DocumentPage child) {
         Utils.clearUntakableView(child);
         LOG.i("onSpaceAvailable:", "fromPage:", child.getNumber());
 
diff --git a/library/src/main/java/com/otaliastudios/printer/PdfPrinter.java b/library/src/main/java/com/otaliastudios/printer/PdfPrinter.java
index 828234e..5e36c64 100644
--- a/library/src/main/java/com/otaliastudios/printer/PdfPrinter.java
+++ b/library/src/main/java/com/otaliastudios/printer/PdfPrinter.java
@@ -47,7 +47,7 @@ public PdfPrinter(@NonNull DocumentView document, @NonNull PrintCallback callbac
     @Override
     public void print(final String printId, @NonNull final File directory, @NonNull String filename) {
         Context context = mDocument.getContext();
-        if (!checkPermission(context)) return;
+        if (!checkPermission(context, directory)) return;
         if (!checkPreview(printId, directory, filename)) return;
         if (!filename.toLowerCase().endsWith(".pdf")) filename += ".pdf";
         final File file = new File(directory, filename);
diff --git a/library/src/main/java/com/otaliastudios/printer/Printer.java b/library/src/main/java/com/otaliastudios/printer/Printer.java
index 57aaade..41b5d89 100644
--- a/library/src/main/java/com/otaliastudios/printer/Printer.java
+++ b/library/src/main/java/com/otaliastudios/printer/Printer.java
@@ -7,12 +7,16 @@
 import android.content.ContextWrapper;
 import android.content.pm.PackageManager;
 import android.os.Build;
+import android.os.Environment;
 import android.support.annotation.CallSuper;
 import android.support.annotation.NonNull;
 import android.view.ViewTreeObserver;
 
 import java.io.File;
 import java.io.IOException;
+import java.net.URI;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 
 /**
  * A general interface for engines that can print view hierarchies to some sort or file or folder.
@@ -57,7 +61,16 @@ public void onGlobalLayout() {
         return true;
     }
 
-    boolean checkPermission(Context context) {
+    boolean checkPermission(Context context, File directory) {
+        // Check external permissions... But only if the directory is external.
+        // For external dirs, this still implies that the developers add the permissions to their manifest.
+
+        // Could be better, but anyway..
+        File ext = Environment.getExternalStorageDirectory();
+        if (!directory.getAbsolutePath().startsWith(ext.getAbsolutePath())) {
+            return true; // Not external
+        }
+
         if (Build.VERSION.SDK_INT < 23) return true;
 
         String[] permissions = new String[2];
diff --git a/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentEditText.java b/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentEditText.java
index d5060f8..4c40d7e 100644
--- a/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentEditText.java
+++ b/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentEditText.java
@@ -6,7 +6,7 @@
 import android.support.v7.widget.AppCompatEditText;
 import android.util.AttributeSet;
 
-import com.otaliastudios.printer.DocumentTextHelper;
+import com.otaliastudios.printer.DocumentHelper;
 import com.otaliastudios.printer.DocumentView;
 
 /**
@@ -15,7 +15,7 @@
  * Don't use if you don't have appcompat in your classpath.
  *
  * @see AppCompatDocumentTextView
- * @see DocumentTextHelper
+ * @see DocumentHelper
  */
 public class AppCompatDocumentEditText extends AppCompatEditText {
 
@@ -34,6 +34,6 @@ public AppCompatDocumentEditText(Context context, @Nullable AttributeSet attrs,
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
         super.onLayout(changed, left, top, right, bottom);
-        DocumentTextHelper.onLayout(this);
+        DocumentHelper.onLayout(this);
     }
 }
diff --git a/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentTextView.java b/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentTextView.java
index 1a86b0c..2aa5d5b 100644
--- a/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentTextView.java
+++ b/library/src/main/java/com/otaliastudios/printer/view/AppCompatDocumentTextView.java
@@ -6,9 +6,8 @@
 import android.support.v7.widget.AppCompatTextView;
 import android.util.AttributeSet;
 
-import com.otaliastudios.printer.DocumentTextHelper;
+import com.otaliastudios.printer.DocumentHelper;
 import com.otaliastudios.printer.DocumentView;
-import com.otaliastudios.printer.view.AppCompatDocumentEditText;
 
 /**
  * A {@link android.support.v7.widget.AppCompatTextView} implementation that works well when
@@ -16,7 +15,7 @@
  * Don't use if you don't have appcompat in your classpath.
  *
  * @see AppCompatDocumentEditText
- * @see DocumentTextHelper
+ * @see DocumentHelper
  */
 public class AppCompatDocumentTextView extends AppCompatTextView {
 
@@ -35,6 +34,6 @@ public AppCompatDocumentTextView(Context context, @Nullable AttributeSet attrs,
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
         super.onLayout(changed, left, top, right, bottom);
-        DocumentTextHelper.onLayout(this);
+        DocumentHelper.onLayout(this);
     }
 }
diff --git a/library/src/main/java/com/otaliastudios/printer/view/DocumentEditText.java b/library/src/main/java/com/otaliastudios/printer/view/DocumentEditText.java
index b7ea614..71a8a52 100644
--- a/library/src/main/java/com/otaliastudios/printer/view/DocumentEditText.java
+++ b/library/src/main/java/com/otaliastudios/printer/view/DocumentEditText.java
@@ -8,16 +8,15 @@
 import android.util.AttributeSet;
 import android.widget.EditText;
 
-import com.otaliastudios.printer.DocumentTextHelper;
+import com.otaliastudios.printer.DocumentHelper;
 import com.otaliastudios.printer.DocumentView;
-import com.otaliastudios.printer.view.DocumentTextView;
 
 /**
  * An {@link EditText} implementation that works well when laid out inside
  * a {@link DocumentView}.
  *
  * @see DocumentTextView
- * @see DocumentTextHelper
+ * @see DocumentHelper
  */
 @SuppressLint("AppCompatCustomView")
 public class DocumentEditText extends EditText {
@@ -42,6 +41,6 @@ public DocumentEditText(Context context, @Nullable AttributeSet attrs, int defSt
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
         super.onLayout(changed, left, top, right, bottom);
-        DocumentTextHelper.onLayout(this);
+        DocumentHelper.onLayout(this);
     }
 }
diff --git a/library/src/main/java/com/otaliastudios/printer/view/DocumentTextView.java b/library/src/main/java/com/otaliastudios/printer/view/DocumentTextView.java
index 945486d..f507fb9 100644
--- a/library/src/main/java/com/otaliastudios/printer/view/DocumentTextView.java
+++ b/library/src/main/java/com/otaliastudios/printer/view/DocumentTextView.java
@@ -8,7 +8,7 @@
 import android.util.AttributeSet;
 import android.widget.TextView;
 
-import com.otaliastudios.printer.DocumentTextHelper;
+import com.otaliastudios.printer.DocumentHelper;
 import com.otaliastudios.printer.DocumentView;
 
 /**
@@ -16,7 +16,7 @@
  * a {@link DocumentView}.
  *
  * @see DocumentEditText
- * @see DocumentTextHelper
+ * @see DocumentHelper
  */
 @SuppressLint("AppCompatCustomView")
 public class DocumentTextView extends TextView {
@@ -41,6 +41,6 @@ public DocumentTextView(Context context, @Nullable AttributeSet attrs, int defSt
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
         super.onLayout(changed, left, top, right, bottom);
-        DocumentTextHelper.onLayout(this);
+        DocumentHelper.onLayout(this);
     }
 }