[3.2.x] Improved pagination documentation

* Link to the topic guide
* Document that page() can raise PageNotAnInteger.

Backport of a57e91adee from master

docs/ref/paginator.txt

@@ -6,6 +6,8 @@ Django provides a few classes that help you manage paginated data -- that is,
 data that's split across several pages, with "Previous/Next" links. These
 classes live in :source:`django/core/paginator.py`.
 
+For examples, see the :doc:`Pagination topic guide </topics/pagination>`.
+
 .. module:: django.core.paginator
    :synopsis: Classes to help you easily manage paginated data.
 
@@ -76,7 +78,9 @@ Methods
 .. method:: Paginator.page(number)
 
     Returns a :class:`Page` object with the given 1-based index. Raises
-    :exc:`InvalidPage` if the given page number doesn't exist.
+    :exc:`PageNotAnInteger` if the ``number`` cannot be converted to an integer
+    by calling ``int()``. Raises :exc:`InvalidPage` if the given page number
+    doesn't exist.
 
 .. method:: Paginator.get_elided_page_range(number, *, on_each_side=3, on_ends=2)