diff --git a/.gitignore b/.gitignore
index 4df656e..5a8ab3c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 Cargo.lock
 _things
 .DS_Store
+.idea/
diff --git a/src/structure.rs b/src/structure.rs
index a5def42..90dc1c3 100644
--- a/src/structure.rs
+++ b/src/structure.rs
@@ -136,6 +136,12 @@ impl<'a> Catalog<'a> {
     pub fn output_intents(&mut self) -> TypedArray<'_, Dict> {
         self.insert(Name(b"OutputIntents")).array().typed()
     }
+
+    /// Start writing the `/AF` array to specify the associated files of the
+    /// document. PDF 2.0+.
+    pub fn associated_files(&mut self) -> TypedArray<'_, FileSpec> {
+        self.insert(Name(b"AF")).array().typed()
+    }
 }
 
 deref!('a, Catalog<'a> => Dict<'a>, dict);