diff --git a/IPython/nbformat/sign.py b/IPython/nbformat/sign.py
index ba16c9a..90e578b 100644
--- a/IPython/nbformat/sign.py
+++ b/IPython/nbformat/sign.py
@@ -263,10 +263,17 @@ class TrustNotebookApp(BaseIPythonApplication):
     description="""Sign one or more IPython notebooks with your key,
     to trust their dynamic (HTML, Javascript) output.
     
+    Trusting a notebook only applies to the current IPython profile.
+    To trust a notebook for use with a profile other than default,
+    add `--profile [profile name]`.
+    
     Otherwise, you will have to re-execute the notebook to see output.
     """
     
-    examples = """ipython trust mynotebook.ipynb and_this_one.ipynb"""
+    examples = """
+    ipython trust mynotebook.ipynb and_this_one.ipynb
+    ipython trust --profile myprofile mynotebook.ipynb
+    """
     
     flags = trust_flags
     
diff --git a/docs/source/notebook/security.rst b/docs/source/notebook/security.rst
index b5d22cd..8a3130f 100644
--- a/docs/source/notebook/security.rst
+++ b/docs/source/notebook/security.rst
@@ -49,6 +49,12 @@ the IPython profile's security directory. By default, this is::
 
     ~/.ipython/profile_default/security/notebook_secret
 
+.. note::
+
+    The notebook secret being stored in the profile means that
+    loading a notebook in another profile results in it being untrusted,
+    unless you copy or symlink the notebook secret to share it across profiles.
+
 When a notebook is opened by a user, the server computes a signature
 with the user's key, and compares it with the signature stored in the
 notebook's metadata. If the signature matches, HTML and Javascript