Updated READMED with documentation about builtin filters.

README.md

@@ -57,6 +57,20 @@ Secretary will handle multiline variable values replacing the line breaks with a
 To be documented...
 
 
+### Builtin Filters
+Secretary includes some predefined *jinja2* filters. Included filters are:
+
+- **markdown(value)**
+Convert the value, a markdown formated string, into a ODT formated text. Example:
+
+        {{ invoice.description|markdown }}
+
+- **pad(value, length)**
+Pad zeroes to `value` to the left until output value's length be equal to `length`. Default length if 5. Example:
+
+        {{ invoice.number|pad(6) }}
+
+
   [1]: http://jinja.pocoo.org/docs/templates/
   [2]: https://github.com/mirkonasato/pyodconverter
   [3]: http://jinja.pocoo.org/docs/api/#jinja2.Environment