diff --git a/src/Tools/Graphview/graph_file.scala b/src/Tools/Graphview/graph_file.scala
--- a/src/Tools/Graphview/graph_file.scala
+++ b/src/Tools/Graphview/graph_file.scala
@@ -1,47 +1,54 @@
 /*  Title:      Tools/Graphview/graph_file.scala
     Author:     Makarius
 
 File system operations for graph output.
 */
 
 package isabelle.graphview
 
 
 import isabelle._
 
 import java.io.{File => JFile}
 import java.awt.{Color, Graphics2D}
 
 
 object Graph_File
 {
   def write(file: JFile, graphview: Graphview)
   {
     val box = graphview.bounding_box()
     val w = box.width.ceil.toInt
     val h = box.height.ceil.toInt
 
     def paint(gfx: Graphics2D)
     {
       gfx.setColor(graphview.background_color)
       gfx.fillRect(0, 0, w, h)
       gfx.translate(- box.x, - box.y)
       graphview.paint(gfx)
     }
 
     val name = file.getName
     if (name.endsWith(".png")) Graphics_File.write_png(file, paint, w, h)
     else if (name.endsWith(".pdf")) Graphics_File.write_pdf(file, paint, w, h)
     else error("Bad type of file: " + quote(name) + " (.png or .pdf expected)")
   }
 
   def write(options: Options, file: JFile, graph: Graph_Display.Graph)
   {
     val the_options = options
     val graphview =
       new Graphview(graph.transitive_reduction_acyclic) { def options = the_options }
     graphview.update_layout()
 
     write(file, graphview)
   }
+
+  def make_pdf(options: Options, graph: Graph_Display.Graph): Bytes =
+    Isabelle_System.with_tmp_file("graph", ext = "pdf")(graph_file =>
+    {
+      write(options, graph_file.file, graph)
+      Bytes.read(graph_file)
+    })
 }