diff --git a/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java b/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java
index b00c6f037f0..41ef23e20ff 100644
--- a/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java
+++ b/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDDocument.java
@@ -1264,6 +1264,7 @@ public void close() throws IOException
             if (signingSupport != null)
             {
                 firstException = IOUtils.closeAndLogException(signingSupport, LOG, "SigningSupport", firstException);
+                signingSupport = null;
             }
 
             // close all intermediate I/O streams
@@ -1281,6 +1282,16 @@ public void close() throws IOException
                 firstException = IOUtils.closeAndLogException(ttf, LOG, "TrueTypeFont", firstException);
             }
 
+            // Release large data structures immediately so the GC can reclaim memory
+            // even if callers hold a reference to this COSDocument instance.
+            fontsToSubset.clear();
+            fontsToClose.clear();
+            documentInformation = null;
+            documentCatalog = null;
+            encryption = null;
+            resourceCache = null;
+            accessPermission = null;
+
             // rethrow first exception to keep method contract
             if (firstException != null)
             {