diff --git a/pyproject.toml b/pyproject.toml
index 7e531ca9..578252c7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,7 +31,8 @@ dependencies = [
   "PyYAML>=6.0.1,<7",
   "toml>=0.10.2,<1",
   "waitress>=2.1.2,<3",
-  "openepub>=0.0.6,<1"
+  "openepub>=0.0.6,<1",
+  "pypdf>=3.17.4"
 ]
 
 [project.scripts]