fix pdf page numbering

private_includes/base/footer_with_songinfo.ily

@@ -242,13 +242,23 @@
       `(line-width . ,(* (chain-assoc-get 'header:songinfo-size-factor props songInfoLineWidthFraction) (ly:output-def-lookup layout 'line-width)))
       arg)))
 
+#(define pdf-encode (@@ (lily framework-ps) pdf-encode))
+% PDF tags
+#(define-markup-command (page-number-to-pdf-label layout props) ()
+     (ly:make-stencil
+      (list 'embedded-ps
+             (ly:format
+              "[ /Label (~a) /PAGELABEL pdfmark\n" (pdf-encode (chain-assoc-get 'page:page-number-string props "?"))))
+      empty-interval empty-interval
+      ))
+
 \paper {
   print-first-page-number = ##t
   first-page-number = #0
 
   oddFooterMarkup = \markup {
     \fill-line {
-      \line { \null }
+      \line { \page-number-to-pdf-label \null }
       \line { \if \on-last-page-of-part \general-align #Y #DOWN \fractional-line-width \print-songinfo }
       \line { \if \should-print-page-number \print-pagenumber }
     }
@@ -257,7 +267,7 @@
     \fill-line {
       \line { \if \should-print-page-number \print-pagenumber }
       \line { \if \on-last-page-of-part \general-align #Y #DOWN \fractional-line-width \print-songinfo }
-      \line { \null }
+      \line { \page-number-to-pdf-label \null }
     }
   }
 }