diff --git a/synapse/media/_base.py b/synapse/media/_base.py
index fc53c357e..6e73da2ef 100644
--- a/synapse/media/_base.py
+++ b/synapse/media/_base.py
@@ -64,6 +64,7 @@ INLINE_CONTENT_TYPES = [
     "text/csv",
     "application/json",
     "application/ld+json",
+    "application/pdf",
     # We allow some media files deemed as safe, which comes from the matrix-react-sdk.
     # https://github.com/matrix-org/matrix-react-sdk/blob/a70fcfd0bcf7f8c85986da18001ea11597989a7c/src/utils/blobs.ts#L51
     # SVGs are *intentionally* omitted.