diff --git a/main.go b/main.go
index 001cacf..4f3cf2d 100644
--- a/main.go
+++ b/main.go
@@ -299,7 +299,11 @@ func servePDF(w http.ResponseWriter, r *http.Request) {
 				return
 			}
 			defer f.Close()
-			w.Header().Set("Content-Type", "application/octet-stream")
+			if ext == ".pdf" || ext == "" {
+				w.Header().Set("Content-Type", "application/pdf")
+			} else {
+				w.Header().Set("Content-Type", "text/plain")
+			}
 			w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, filename))
 			w.Header().Set("Content-Length", fmt.Sprintf("%d", fi.Size()))
 			io.Copy(w, f)