I am writing lecture notes for ordinary differential equations in greek using the book class in Overleaf. Everything was fine (no errors, no warnings) till I included a png picture. Since I included the picture (named 1.png) every letter in chapter's title is giving a warning. I removed a lot of things from the code so that it doesn't get too long.


\title{Συνήθεις Διαφορικές Εξισώσεις}
\chapter{Γραμμικές ή ντετερμινιστικές εξισώσεις }

\includegraphics[width=5.5cm, height=4cm]{1}

The warning I get for the first letterPackage hyperref Warning: Glyph not defined in PD1 encoding, removing\textGamma' on input line 23.`

  • You get warnings not errors. And this is unrelated to graphics: As David wrote, your tex-system/hyperref is probably older and so you need the option unicode. Commented Sep 21, 2021 at 7:20
  • @UlrikeFischer I looked for the version and it says Version 3.14159265-2.6-1.40.21 (TeX Live 2020). What version should I use? Commented Sep 21, 2021 at 8:01
  • 1
    relevant is the hyperref version. With version hyperref 2021-02-27 v7.00k unicode is already the default, the current version is 7.00m Commented Sep 21, 2021 at 8:04
  • @UlrikeFischer Is it possible to load the newest package in Overleaf or I must use for example texmaker ? Commented Sep 21, 2021 at 9:16
  • 1
    overleaf will update to texlive 2021 in the near future. Until then using the unicode option mentioned by David should be fine. Commented Sep 21, 2021 at 9:19

1 Answer 1


It should run without error with a current hyperref but otherwise use


so bookmarks can use Unicode rather than the original PDF string encoding (which does not allow Greek).

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