diff --git a/.readthedocs.yml b/.readthedocs.yml
index e0de75f..905a6cf 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -20,7 +20,8 @@ sphinx:
 #  configuration: mkdocs.yml
 
 # Optionally build your docs in additional formats such as PDF and ePub
-formats: all
+formats: 
+ - pdf
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
diff --git a/requirements.txt b/requirements.txt
index a24b29c..cdc11b6 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -21,11 +21,11 @@ percy-selenium
 coverage
 
 # doc building requirements
-Jinja2==3.0.3
-sphinx==3.*
+Jinja2
+sphinx
 sphinx-tabs
-sphinx-rtd-theme==0.4.*
-sphinx-toolbox==2.15.0
+sphinx-rtd-theme
+sphinx-toolbox
 sphinx-intl
 pywebio_battery