src/Pure/Thy/presentation.scala

     val documents =
       for (doc <- info.documents)
       yield {
         Isabelle_System.with_tmp_dir("document")(tmp_dir =>
         {
+          progress.echo_document("Building document " + session + "/" + doc.name + " ...")
+          val start = Time.now()
+
+
           // prepare sources
 
           val (doc_dir, root) = prepare_dir1(tmp_dir, doc)
           val digests = File.find_files(doc_dir.file, follow_links = true).map(SHA1.digest)
           val sources = SHA1.digest_set(digests).toString

                 "Failed to build document " + quote(doc.name))
             }
             else if (!result_path.is_file) {
               error("Bad document result: expected to find " + root_pdf)
             }
-            else doc.set_sources(sources) -> Bytes.read(result_path)
+            else {
+              val stop = Time.now()
+              val timing = stop - start
+              progress.echo_document("Finished document " + session + "/" + doc.name +
+                " (" + timing.message_hms + " elapsed time)")
+
+              doc.set_sources(sources) -> Bytes.read(result_path)
+            }
           }
         })
       }
 
     for (dir <- doc_output; (doc, pdf) <- documents) {