diff --git a/docs/README.md b/docs/README.md
index cc11c64..5996f99 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -15,4 +15,8 @@ pip3 install -r ../requirements.txt
 make html
 # now you can view the docs in your browser:
 firefox build/html/index.html
+
+# generate pdf version of docs:
+make latex
+make pdflatex
 ````
diff --git a/requirements.txt b/requirements.txt
index a794851..a53c9b7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 alabaster==0.7.12
 appdirs==1.4.3
 attrs==21.2.0
-Babel==2.9.0
+Babel==2.9.1
 CacheControl==0.12.6
 certifi==2019.11.28
 chardet==3.0.4